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In addition to setting the AQL, the buyer should choose the inspection level. The
difference between the inspection levels listed below is the number of samples to
inspect.
Normal inspection(or level-II inspection):It is the default level, and it is chosenfor 90! of inspections.
ISO 2859 definition for normal inspection:
"#ormal inspection is used when there is no reason to suspect that the $%uality level&
differs from an acceptable level.'
"(nless otherwise specified, level II shall be used. Level I may be used when less
discrimination is needed or level III when greater discrimination is re%uired.'
Ti!tened inspection (or level-III inspection):more samples are chec)ed. This
inspection level is used for suppliers that recently had severe %uality problems, or for
high*value products.
ISO 2859 definition for ti!tened inspection:
"(se of a sampling plan with an acceptance criterion that is tighter than that for the
corresponding plan for normal inspection.'
"ed#ced inspection (or level-I inspection): less samples are inspected. This
inspection level is appropriate when the client is confident that the %uality of the
products is acceptable.
Note:it is never appropriate for a re*inspection following a refusal.
ISO 2859 definition for red#ced inspection:
"The discriminatory ability under reduced inspection is less than under normal
inspection.'
There are also four other "special' inspection levels. They are used in cases where the
inspector can only chec) very few samples. +owever, the ris) of accepting products of
bad %uality is higher.
or e-ample if the inspector has to do a very particular chec)ing that ta)es him a long
time per product /e.g. dismantling a radio system to see all the components, chec) the
welding1.
Another e-ample if a particular test ends up in destruction of the product /e.g. undoing
the stitching of a garment to chec) the cut pieces against the client2s patterns1.
ISO 2859 definition for special inspection levels:
"our additional special levels, 3*4, 3*5, 3*6 and 3*7 $& may be used where relatively
small sample si8es are necessary and larger sampling ris)s can be tolerated.'
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How to determine the correct quantity and acceptable fault levels
when inspecting a product
How to determine the quantity to be inspectedWhile we all would like to have every single unit of goods to be inspected, this is simply not
practicable or affordable for most products and companies.
The best approach, which is recommended by International Standards Agencies such as ANSI/
ASQ, is to use the AQL (Acceptable Quality Limit or Level) approach to determine both the sample
inspection size and the levels required to determine of an Inspection is a Pass or a Fail.
We use the internationally recognized Acceptable Quality Limit (AQL) standard for all product
inspections. For each inspection, this allows the client to set their acceptable quality tolerance levels.
What is AQL (Acceptable Quality Limit or Level)?
AQL is sometimes called Acceptable Quality Limit by some people or Acceptable Quality Level by
others. They both essentially mean the same thing.
To determine the AQL level of a product you need to use the measure table that is recommended by
ISO 2859, NF06-022, DIN 40080, BS 6001, ANSI/ASQC Z1.4.
This table allows you to determine the sample size (amount or quantity) that should be taken from an
order or batch to be inspected or tested. It then provides you with the values to determine whether a
product has met the buyers specifications and passes or fails the inspection.
You can then determine the tolerance levels in terms of Critical, Major and Minor levels for your
product. The tolerance levels is a fair and equitable method which gives the seller and the buyer
leeway to determine what is an Pass or Fail for an order.
The way to determine these are below:
Critical defects(totally unacceptable: a user might get harmed, or regulations are not
respected) 0% e.g. plug on an electrical device and it smokes, or a non-welded bar in a bed The
product is dangerous
Major defects(these products would usually not be considered acceptable by the end user)
usually 2.5% e.g. scratches that are noticeable and may prevent the product being sold
Minor defects(there is some departure from specifications, but most users would not mind
it). usually 4.0% e.g. a small scratch on the bottom of a leg of a bed, or on non-visual piece on an
electrical appliance
All Inspection reports generated by the inspection companies listed on Goodada.com will clearly
display the AQL standards and show you if the production has failed or passed.
How do I calculate the correct sample size and acceptance value?
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For the majority of products the best suggestion is to use a Standard Level II. If this is the accepted
Level then the table below will provide the sample size, critical, major and minor vales (acceptable
value) see the page below
Lot Size Sample
Size
Critical
Defects
Major
Defects
Minor
Defects
2-8 20 0 0
9-15 30 0 0
16-25 50 0 0
26-50 80 0 1
51-90 130 1 1
91-150 200 1 2
151-280 320 2 3
281-500 500 3 5
501-1200 800 5 7
1201-3200 1250 7 10
3201-10000 2000 10 14
10001-35000 3150 14 21
35001-150000 5000 21 21
150001-500000 8000 21 21
500000 and oer 12500 21 21
For any non-standard products, or products where the buyer requires a more detailed inspection,
please refer to the tables below.
Our inspectors would be delighted to assist you to determine the correct levels, sample size and
acceptance numbers
Sample Size Chart this will allow you to determine the amount or quantity of your sample
Lot Size General Inspection Levels Specific Inspection Levels
I II III S-1 S-2 S-3 S-4
2-8 A A B A A A A
-15 A B ! A A A A
1"-25 B ! # A A B B
2"-50 ! # $ A B B !
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51-0 ! $ % B B ! !
1-150 # % G B B ! #
151-280 $ G & B ! # $
281-500 % & ' B ! # $
501-1200 G ' ( ! ! $ %
1201-3200 & ( L ! # $ G
3201-10000 ' L ) ! # % G
10001-35000 ( ) * ! # % &
35001-150000 L * + # $ G '
150001-500000 ) + , # $ G '
500000 an over * , . # $ & (
Use the letter identified in the Sample Size Chart to determine the Acceptance Values and
Sample Size
Code
Letter
Sample
Size
Standard
Major
Standard
Minor
1!0" 1!5" 2!5" #!0" 6!5"
$ 2 0 0 0 0 0
% 3 0 0 0 0 0
C 5 0 0 0 0 1
D 8 0 0 0 1 1
& 13 0 0 1 1 2
' 20 0 1 1 2 3
( 32 1 1 2 3 5
) 50 1 2 3 5 7
* 80 2 3 5 7 10
+ 125 3 5 7 10 14
L 200
5 7 10 14 21
M 315 7 10 14 21 21
, 500 10 14 21 21 21
800 14 21 21 21 21
. 1250 21 21 21 21 21
/ 2000 21 21 21 21 21
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2013 Green Dragon International Ltd (Republic of Ireland)
What is an inspection level inISO 2859-1 and ANSI/ASQC
Z1.4?
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This article introduces the different options available to
buyers, when it comes to the representativity of inspection findings.
Inspection level II (under normal severity) is appropriate for most inspections. But it is
sometimes necessary to increaseor or reducethe number of samples to check.
The need for sampling, rather than
100% checking
When controlling the quality of a batch of products, it is not practical to inspect 100% of
them (unless the quantity is very small). Inspecting a large number of products takes a
long time: it is expensive, and inspectors are less effective as they get tired. Actually, a
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100% check does not yield that much more information than inspecting a statistically
representative sample.
The question becomes: how many products to check?
Why different inspection levels?
There is a fairly obvious principle in statistical quality control: the greater the order
quantity, the higher the number of samples to check.
But should the number of samples ONLY depend on the order quantity? What if this
factory had many quality problems recently, and you suspect there are many defects? Inthis case, you might want more products to be checked.
On the other hand, if an inspection requires tests that end up in product destruction,
shouldnt the sample size be drastically reduced? And if the quality issues are always
present on all the products of a given batch (for reasons inherent to processes at work),
why not check only a few samples?
For these reasons, different levels are proposed by MIL-STD 105 E (the widely
recognized standard for statistical quality control).
It is usually the buyers responsibility to choose the inspection levelmore samples to
check means more chances to reject bad products when they are bad, but it also
means more days (and dollars) spent in inspection.
The 3 general inspection levels
Level I
Has this supplier passed most previous inspections? Do you feel confident in their
products quality? Instead of doing no quality control, buyers can check less samples by
opting for a level-I inspection.
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However, settling on this level by default, in order to spend less time/money on
inspections, is very risky. The likelihood of finding quality problems is lower than
generally recommended.
Level II
It is the most widely used inspection level, to be used by default.
Level III
If a supplier recently had quality problems, this level is appropriate. More samples are
inspected, and a batch of products will (most probably) be rejected if it is below the
quality criteria defined by the buyer.
Some buyers opt for level-III inspections for high-value products. It can also be
interesting for small quantities, where the inspection would take only one day whatever
the level chosen.
The 4 special inspection levels
These special levels can be applied in cases where only very few samples can bechecked. Four additional special levels, S-1, S-2, S-3 and S-4 [] may be used where
relatively small sample sizes are necessary and larger sampling risks can be tolerated
(ISO 2859 standard).
Under S-3 level, the number of samples to check is lower than under S-4, and so on.
In practice: for consumer goods, quality control is usually performed under the general
levels.
The special levels are used only for certain tests that either take lots of time or destroy
the samples. Another situation where special levels are appropriate is a container-
loading supervisionto have an idea of what is inside the cartons, without spending too
much time at that checking.
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Two examples to get an clearer
understanding
Lets say you have ordered 5,000 pcs of a product. In the table below, you can see how
many samples would be drawn under each of the 7 inspection levels.
General inspection levels Special inspection levels
I II III S-1 S-2 S-3 S-4
80pcs 200pcs 315pcs 5pcs 8pcs 20pcs 32pcs
As you can see, the numbers of samples to check vary from 5pcs to 315pcs. But a
trained inspector might be able to do it in one day, whatever the inspection level you
choose.
Now lets say you have ordered 40,000pcs of a product. Again, you can see the
differences in sample sizes.
General inspection levels Special inspection levels
I II III S-1 S-2 S-3 S-4
200pcs 500pcs 800pcs 8pcs 13pcs 32pcs 80pcs
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In this case, the inspection might take one day of work (for S-1, S-2, S-3, S-4, or
reduced level), two days (under level II), or three days (under level III).
What is the AQL, and when it isapplicable?
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The AQL tables are statistical tools at the disposal of
buyers (for product inspections). They are an industry standard. Most suppliers involved
in international trade are familiar with it.
They help determine two key elements:
How many samples should be picked and inspected, among a batch of product or parts?
Where is the limit between acceptability and refusal, when it comes to defective
products?
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The need for an objective
measurement of quality
In certain product categories, there will be defective products in virtually every
production batch. It is often true even after the manufacturer has checked each
individual product and has repaired the defective ones, since visual inspection is not
100% reliable.
Therefore, in many supplier/buyer relationships (particularly when the application does
not result in life or death outcomes), the supplier is not expected to deliver defect-
free goods. The buyer needs to control the quality of purchased goods, since he does
not wanttoo manydefects. But what does too many mean?
How to set the limit between acceptability and refusal in a way that can be agreed upon
and measured?
Definition and application of AQL
The limit, as described above, is called the AQL. It stands for Acceptance Quality Limit,
and is defined as the quality level that is the worst tolerable (source:ISO 2859-1
standard).
For example: I want no more than 1.5% defective items in the whole order quantity, on
average over several production runs with that supplier means the AQL is 1.5%.
In practice, three types of defects are distinguished. For most consumer goods, the
limits are:
0% for critical defects (totally unacceptable: a user might get harmed, or regulations are
not respected).
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=1141http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=1141http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=1141http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=1141 -
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2.5% for major defects (these products would usually not be considered acceptable by
the end user).
4.0% for minor defects (there is some departure from specifications, but most users
would not mind it).
These proportionsvaryin function of the product and its market. Components used in
building an airplane are subject to much lower AQL limits.
Note that this tool is used mostly during final outgoing inspections (when the products
are ready to be shipped out), and sometimes during production (when the number of
products is sufficient to have an idea of the batchs average quality).
Getting familiar with the AQL tables
Before using the AQL tables, you should know three parameters:
The lot size. If you ordered different products, the quantity of each product is a lot size,
and it is advised to perform separate inspections for each lot. If you ordered only one
product, the lot size is the total batch quantity.
Theinspection level. Different inspection levels will command different numbers of
samples to inspect. In this article, we will stick to the so-called level II under normal
severity and to single sampling plans.
The AQL level appropriate for your market. If your customers acceptvery few defects,
you might want to set a lower AQL for both major and minor defects.
There are basically two tables. The first one tells you which code letter to use. Then,
the code letter will give you the sample size and the maximum numbers of defects that
can be accepted.
First table: sample size code letters
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How to read this table?
If you follow my example, I assume your lot size is comprised between 3,201 pcs and
10,000 pcs, and that your inspection level is II. Consequently, the code letter is L.
Second table: single sampling plans for level II inspection (normal severity)
How to read this table?
Your code letter is L, so you will have to draw 200 pcs randomly from the total lot size.
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Besides, I assume you have set your AQL at 2.5% for major defects and 4.0% for minor
defects. Therefore, here are the limits: the products are accepted if NO MORE than 10
products with major defects AND NO MORE than 14 products with minor defects are
found.
For example, if you find 15 products with major defects and 12 products with minor
defects, the products are refused. If you find 3 with major defects and 7 with minor
defects, they are accepted.
Note: inquality inspections, the number of defective products is only one of the criteria.
It is sometimes called quality, or quality findings. The other criteria are usually on the
inspectors checklist, which typically includes:
Packaging conformity (barcodes, inner packing, cartons, shipping marks).
Product conformity (aspect, workmanship). If all the products are in red color instead
of orange, there is no need to count each sample as a defect. It makes more sense to
refuse for product conformity.
Specific tests defined in the inspection checklist (they might not be performed on all
inspected samples if they are time-consuming or destructive).
Frequently Asked Questions about
AQL
Q: So, basically I have to authorize the factory to
produce some defects?
A: In theory no. Thats why the AQL was renamed, from acceptable quality level to
acceptance quality limit. It is a limit (and a loose one at that).
Here is what the ISO2859 standard says:
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Although individual lots with quality as bad as the acceptance quality limit may be
accepted with fairly high probability, the designation of an acceptance quality limit does
not suggest that this is a desirable quality level. Sampling schemes [] are designed to
encourage suppliers to have process averages consistently better than the AQL.
Note that, in practice, using these statistics means you assume the factory cannot
reasonably be expected to turn out 100% good quality.
Alternatively, you can choose an acceptance on zero plan. As soon as one defect is
found, the inspection is failed. But you can impose this to suppliers only in situations
where quality requirements are very high (in the auto industry, in aerospace).
Q: Based on my AQL, I calculated the proportion ofdefects authorized. Why dont they correspond to the
maximum number of defects authorized?
A: It is true. In our example above, 2.5% of 200 samples is 5 samples, but we accept the
goods even if 10 samples are found with a major defect.
Why this difference? There are heavy statistics behind this issue. To keep it simple, theproducers risk is his risk of rejection (based on the random element when drawing the
sample) even though his products (if they were all checked) would be accepted. That
risk is about 5% in this standard. And, along the same logic, there is a consumers risk
and is is around 10%. As you can see, this standard is favorable to the producers side.
Q: Why not just say, well check 10% of the quantity,
or whatever percentage deemed appropriate?
A: Here again, the statisticians tell us it is not that simple. As we go up in the total
quantity, the proportion of products checked can decrease,for the same confidence in
the inspection results.
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As you can see in the chart below, the number of samples to check (vertical axis)
increases at a slower pace than the total quantity (horizontal axis).
Q: How to choose an AQL limit for my products?
A:See this article. It depends on your distribution channel and your products end
use. Note that your supplier might refuse AQL limits they estimate as too tight (i.e. too
low).
Q: What are the reduced and tightened severities?
A: They are designed to be used in very specific situations, when a producer is
particularly reliable, or on the contrary fails too often.
In practice, these severities are seldom used. Most inspections are done in normal
severity. Thats unfortunate, because the rules to switch from normal to reduced or
tightened are considered a very important part of the standard (actually the evolutions of
these rules constituted the main changes from MIL-STD 105A and MIL-STD 105E).
Q: What are the limits of a quality control approach
based on random sampling and AQL limits?
A: There are several limits:
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1. An AQL limit is a target rather than a maximum. The buyer might have a nasty
surprise when receiving a batch of products that passed the inspection.Read more in
this article.
2. A statistical QC approach does nothing to reduce the defects in the first place.Read
more in this article.
Q: Where can I learn more about the AQL?
If you really want to understand the concept of the AQL, you should spend about 20
minutes (total) watching these 3 videos on Youtube.
How to Read the AQL Tables
When Applying the AQL tables Does or Doesnt Make Sense
Why the AQL tables are not in favor of the buyer
The Special Inspection Levels in
the AQL Tables
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A few years ago I wrote about theinspection levels, but
some people are still confused about the special levels (S1, S2, S3, and S4).
http://www.qualityinspection.org/limits-quality-inspections/http://www.qualityinspection.org/limits-quality-inspections/http://www.qualityinspection.org/quality-expensive/http://www.qualityinspection.org/quality-expensive/http://www.youtube.com/watch?v=hFscyKpA4n0http://www.youtube.com/watch?v=p6hyBDi1Y7Mhttp://www.youtube.com/watch?v=8bUe8nQpI0shttps://qualityinspection.org/special-inspection-levels/https://qualityinspection.org/special-inspection-levels/https://qualityinspection.org/special-inspection-levels/https://qualityinspection.org/special-inspection-levels/http://www.qualityinspection.org/inspection-level/http://www.qualityinspection.org/limits-quality-inspections/http://www.qualityinspection.org/limits-quality-inspections/http://www.qualityinspection.org/quality-expensive/http://www.qualityinspection.org/quality-expensive/http://www.youtube.com/watch?v=hFscyKpA4n0http://www.youtube.com/watch?v=p6hyBDi1Y7Mhttp://www.youtube.com/watch?v=8bUe8nQpI0shttps://qualityinspection.org/special-inspection-levels/https://qualityinspection.org/special-inspection-levels/https://qualityinspection.org/special-inspection-levels/http://www.qualityinspection.org/inspection-level/ -
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Here is what theISO 2859-1 standardsays (emphasis mine):
The inspection level designates the relative amount of inspection. Three inspection
levels, I, II and III, are given in Table 1 for general use. Unless otherwise specified, level
II shall be used. Level I may be used when less discrimination is needed or level III
when greater discrimination is required.Four additional special levels, S-1, S-2, S-3
and S-4are also given in Table 1 andmay be used where relatively small sample
sizes are necessary and larger sampling risks can be tolerated.
Here are a few examples where these special levels come in handy:
You want to check the packaging in full, but only on a few cartons.
You want to perform some time-consuming tests (e.g. a full function test on an electrical
product), and you dont have time to run these tests on all the samples you inspect
visually (in level II, usually).
You want to perform destructive tests (e.g. inspecting bullets by firing them), and
obviously you dont want to destroy too many samples.
How to read the AQL tables whenusing special inspection levels
Short answer:it works just the same as general levels, as I describedbefore.
Long answer:I am going to walk you through an example.
Lets say you are buying 50,000 salt & pepper sets in ceramic.
There are several color combinations, some booklets are included, etc. which means
many ways the packing can go wrong. So you want to check the packing in great detail,
but only on an S3 level.
In the table below, you see that the code letter is G.
http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=1141http://www.qualityinspection.org/what-is-the-aql/http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=1141http://www.qualityinspection.org/what-is-the-aql/ -
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Then lets go to the other table, and you can find this information:
You should check the packing on 32 samples.
If you dont want to accept a defective packing on more than 1.5% of the quantity, the
limit is 1.
In other words, you accept the batch (as far as packing conformity is concerned) if you
find 0 or 1 defective cartons. And you reject it if you find 2 or more.
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Note that, when it comes to tests on products and these tests are conducted on a
special level, they are considered critical (i.e. they are failed as soon as 1 sample
fails).
It makes things more simple and avoids lengthy discussions with Chinese suppliers who
dont fully understand how the statistics work.
I hope this explanation was clear. Questions are welcome in the comment section.
Sampling by Attributes Using theANSI/ASQ Z1.4-2008 Stanar !
I"#By
Eugenie Webster (Klebni!ova"
#ov 24$ 2013 12%3& p' S)
Peer Reviewed: Sampling
The views and opinions expressed in this paper are those of the individual author and
should not be attributed to any company with which the author is now or has been
employed or affiliated.
Abstract
This paper discusses the application of American National Standards Institute
(ANSI)/American Society for Quality (ASQ) Z1.4!""#$Sampling Procedures and
Tables for Inspection by Attributes. It pro%ides simple instructions on ho& to correctly
select the samplin' plan ased on the population sie and the acceptale ris*. In
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addition+ this paper pro%ides a 'eneral o%er%ie& of statistics ehind the de%elopment of
samplin' plans. The intent of this paper is to present a ,uic* refresher on samplin' y
attriutes usin' the ANSI/ASQ Z1.4 !""# standard and to educate a reader on the
common mista*es users ma*e durin' the use of this standard.
Introduction
Attriute samplin' plans are often used to inspect the effecti%eness of the
product/process and to determine the rate of compliance &ith estalished criteria. It is a
common pharmaceutical industry practice to employ American National Standards
Institute (ANSI)/American Society for Quality (ASQ) Z1.4!""#$Sampling Procedures
and Tables for Inspection by Attributesfor inspection of product/process defects.
ANSI/ASQ Z1.4!""#$Sampling Procedures and Tables for Inspectionby Attributesis
an acceptance samplin' system that pro%ides ti'htened+ normal+ and reduced plans to
e applied for attriutes inspection for percent nonconformin' or nonconformities per
1"" units. The use of samplin' tales pro%ides a ,uic*er &ay of selectin' the samplin'
plan instead of de%elopin' a samplin' plan usin' comple- statistics. The standard
pro%ides instructions on ho& it is supposed to e applied ho&e%er+ it is often
misinterpreted. The common mista*es include+ ut not are limited to+ the selection of
incorrect samplin' sie+ selection of incorrect acceptance criteria+ or attriute plan used
for %ariale data+ etc. Therefore+ it is %ery important to properly interpret the standard
and apply the inspection rules as they are prescried. Incorrect application can result in
re'ulatory oser%ations.
The Importance of Sampling
Samplin' is a re'ulatory re,uirement in the pharmaceutical industry. The current 'ood
manufacturin' practice (c0) re,uires samplin' plans to e defined as &ell as
samples to e representati%e of the population and ased on appropriate statistical
criteria. 2or instance+ as per Code of Federal egulations Title !CF" #$Part#$$.$%&(d)+
3Acceptance criteria for the samplin' and testin' conducted y the ,uality control unit
shall e ade,uate to assure that atches of dru' products meet each appropriate
specification and appropriate statistical ,uality control criteria as a condition for their
appro%al and release. The statistical ,uality control criteria shall include appropriate
acceptance le%els and/or appropriate reection le%els.5
Acceptance inspection is performed at many sta'es in the pharmaceutical process+ from
testin' ra& materials to the final pac*a'in' sta'e. Acceptance testin' is necessary since
1""6 inspection is not practical and &ould e %ery costly. In acceptance testin' y
attriutes+ a sample is randomly ta*en and inspected a'ainst estalished specifications
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(allo&ale numer of defects). If the numer of defects e-ceeds the allo&ale numer of
defects+ then the entire lot is reected.
ANSI/ASQ Z1.4-!!"Sampling For Attributes
ANSI/ASQ Z1.4!""#$Sampling Procedures and Tables for Inspection by Attributesisone of the most fre,uently used plans y many pharmaceutical companies as &ell as
other industries. It is reco'nied y the 7S 2ood and 8ru' Administration and 9ealth
:anada. The standard pro%ides %arious inspection plans &ithout 'ettin' into comple-
statistics.
The standard is intended for inspection of final product+ components and ra& materials+
materials in process+ and data and records.
Acceptance samplin' procedures ecame popular durin' ;orld ;ar II. Samplin' plans+
such as 0I
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inspection is applied+ ti'htened inspection can e implemented &hen t&o out of fi%e or
fe&er consecuti%e lots failed normal inspection. ;hen ti'htened inspection is applied+
normal inspection can e implemented &hen fi%e consecuti%e lots pass the ti'htened
inspection. The reduced inspection can e used conditionally &hen the normal
inspection passes for more than t&o consecuti%e lots. Inspection can e discontinued
&hen 1" consecuti%e lots remain on ti'htened inspection. The s&itchin' rule dia'ram is
pro%ided elo&.
&igure 1' S(itching Inspection %ules.
Sampling )lan T*pes
Three types of samplin' plans are pro%ided$ sin'le+ doule+ or multiple. 2i'ure !
outlines the differences of each plan.
&igure ' T*pes of Sampling )lans.
Single *ouble Sa'pling lan +ultiple Sa'pling lan
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Sa'pling
lan
Thisplan isbased onaccepting orrejecting thelot on onesample only.
These plans combine singlesample plans. With double samplingplans, there are three diferentconclusions: accept the lot, rejectthe lot, and resample the lot. I thelot is resampled, the results arecombined with the rst sample. new ccept!"eject le#el number isdetermined with the secondsampling. t the end o the secondsample the lot is then eitheraccepted or rejected.
$imilar to doublesampling, there may be manysampling se%uences todetermine whether to accept orreject the lot. lthoughcomplicated, initially, they mayutili&e smaller sample si&es toaccept the lot. 'owe#er, ithere are rejects, then multiplesampling plans become #erycomplicated.
Inspection )rocedure
The 'eneral procedure (2i'ure @) in desi'nin' the samplin' plan is the follo&in'.
&igure +' Inspection )rocedure.
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Table I' Table I Sample Si,e #etter odes
Lot or %atc Size
Special nspection Leels (eneral nspection Leels
S-1 S-2 S-3 S-#
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2 to 8 A A A A A A B
to 15 A A A A A B !
1" to 25 A A B B B ! #
2" to 50 A B B ! ! # $
51 to 0 B B ! ! ! $ %
1 to 150 B B ! # # % G
151 to 280 B ! # $ $ G &
281 to 500 B ! # $ % & '
501 to 1200 ! ! $ % G ' (
1201 to 3200 ! # $ G & ( L
3201 to 10000 ! # % G ' L )
10001 to 35000 ! # % & ( ) *
35001 to 150000 # $ G ' L * +
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:aution$ Note+ the samplin' plan consists of a sample sie and acceptance criteria at
particular AQ
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The inspection procedure should include the samplin' plan &ith inspection le%el+ type+
and accept/reect criteria. 2or instance+ if the e-pected pac*a'in' lot sie is @D+"""
ottles+ it &ould e impossile to test all @D+""" ottles+ so a representati%e samplin'
sie should e selected. To determine an inspection sample sie+ ANSI/ASQ Z1.4
!""#Sampling by Attributes Plan' (eneral Inspection II' Tightened Plancan e used.
A lot of @D+""" ottles corresponds to letter N (eneral Inspection
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&igure 4' alculating inomial 0istributing 6sing 79cel.
2i'ure = sho&s the ?: constructed y plottin' a %s. p.
&igure :' 2 ur$e onstructed 6sing 79cel.
As sho&n in 2i'ure =+ the proaility of acceptin' a lot containin' !6 defecti%es is D#6
(i.e.+ out of 1"" lots+ it is e-pected to accept D# and reect @! &hen the sample sie is 1""
and the acceptance numer is t&o).
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&igure ;' 2 ur$e for n"6 of the time inspectin' fi%e samples+ #!6 of the time inspectin' 1"
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samples+ DF6 of the time inspectin' !" samples+ and 1@6 of the time inspectin' 1""
sample. ;ith more samples &e test+ the proaility of acceptin' a lot &ith defects
decreases. Thus if &e claim that &e accept ero defects and test a %ery small sample+ in
this case fi%e samples+ there is a hi'h proaility that &e are acceptin' defects in the lot
&ithout ein' ale to detect them.
&igure "' 2perating haracteristic ur$e.
Summar*
In summary+ correct statistical samplin' is re,uired y the pharmaceutical industry
re'ulations. 7nderstandin' of ANSI samplin' y attriutes and correct application &ill
help to a%oid samplin' mista*es and potential oser%ations.
Acron*m #isting
AQ# A%era'e Quality
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?eneral %eferences
ASQ+ ANSI/ASQ Z1.4!""#$Sampling Procedures and Tables for Inspection by
Attributes+ !""#.
Code of Federal egulations+ Title !1+ 2ood and 8ru's (o%ernment rintin' ?ffice+;ashin'ton+ 8:)+ art !11.
G. Stephens+ The )andboo* of Applied Acceptance Sampling+ Plans' Procedures' and
Principles+ ASQ Quality ress+ !""1.
Quality control tools - faq
Can you briefly present your company?
sia (uality )ocus is a Western *rd party inspection company ocusing on %uality control and %uality
assurance in sia. We speciali&e and are e+perts in product inspections, actory audits and product
testing. We can inspect any order and audit any actory within -', anywhere in Bangladesh, India,
a/istan, 0hina, Taiwan, 1ietnam and Thailand.
Why do I need Quality Control ?
We suggest you to #iew our presentation: 23 tips or (uality 0ontrol, and then see i you are loo/ing or
answering to one o the ollowing %uestion:
Is my actory ollowing international and local rules and regulations4 5Social Audit)
'as production started correctly4 5First Article inspection)
Is my order produced according to my specications4 5Product Inspection)
Is the container well loaded4 5Container Loading Inspection)
'ow to ma/e sure there are no deects4 5Defect Sorting Service)
'ow to ensure the actory introduces the right %uality chec/s4 (Production Monitoring)
How do I get started? ,egister onlinein order to create your pri#ate account on our website6 it is ree o charge
and re%uires no commitment.
ter acti#ation o your account, you will be able to choose your desired ser#ice and pro#ide us
with your re%uirements, instructions, specications, criteria and attachments online 57!89.
http://www.slideshare.net/qualityfocus/10-tips-for-quality-controlhttp://www.slideshare.net/qualityfocus/10-tips-for-quality-control -
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ur perations team will prepare, coordinate and arrange your boo/ed ser#ice and you will
recei#e a conrmation email. I you ha#e any %uestions, you can contact us at any time.
The day o the re%uested ser#ice you will recei#e your ully illustrated report by email and it
will also be posted on your secured pri#ate account.
;ou will recei#e one in#oice per month, at the end o the month 5howe#er, i it is your rst time
wor/ing with us we as/ you to pay in ad#ance9.
Register now!
Why should I choose Asia Quality Focus? Epertise%we ocus on consumer products.
+anage'ent%Both Western < local teams.
ersonali.ation%custom=made solutions when needed.
/leibilit%only 7 days notice needed, online boo/ing < trac/ing.
eaper%our ee is >7?- per @an=Aay 52 inspector ! 2 day9.
/aster%easy online boo/ing, re results, $ame=day "eports.
Saer%our ser#ices adhere to recogni&ed international standards: I$7-?, I$?333, $-333
eicate an eperience tea'o inspectors, auditors and engineers.
"ead more aboutsia (uality )ocus
Do you offer sourcing services to find suppliers and
manage projects?
We o not oer an sourcing services6 ll inormation about our clientCs #endors and actories is
condential and shall not be transmitted to any other party. ll inormation shall not be sold or used or
any other purpose than the %uality control ser#ice you are paying or. I you are in need o these
ser#ices, please consult our Dndorsed partners page or rele#ant company inormation.
http://www.asiaqualityfocus.com/user/registerhttp://www.asiaqualityfocus.com/about-aqf/our-companyhttp://www.asiaqualityfocus.com/about-aqf/our-companyhttp://www.asiaqualityfocus.com/user/registerhttp://www.asiaqualityfocus.com/about-aqf/our-company -
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Can I discuss with you in detail my criteria and my product
specifications?
course, and we in#ite you to contact usin order to e+plain your %uality needs.
What information does your inspection report include?
ur reports are #ery detailed, illustrated with pictures and co#er the ollowing:
roduct appearance 5(E9, wor/manship %uality
roduct specications re#iew: %uantity, material, color, si&e, measurements, labeling *3 surcharge.
Who will approve or reject the shipment?
We inspect the shipment according to (Einternational standards and also according to your
instructions, specications and criteria. Then, our results are gi#en to you through a ully detailed and
illustrated report, which should allow you to decide whether to allow the shipment o your products.
;ou can accept or reject your shipment directly online.
Which areas do you cover?
sia (uality )ocus pro#ides %uality controland %uality assurance ser#icesin 2 countries in sia: rom
Indonesia to a/istan and rom 0hina to Thailand.
"ead more about our co#erage area in sia. We always suggest to contact us minimum - hours prior
to the desired inspection date or nal cost conrmation.
http://www.asiaqualityfocus.com/about-aqf/contact-ushttp://www.asiaqualityfocus.com/useful-corner/product-inspection-standardshttp://www.asiaqualityfocus.com/useful-corner/product-inspection-standardshttp://www.asiaqualityfocus.com/inspection-serviceshttp://www.asiaqualityfocus.com/factory-auditshttp://www.asiaqualityfocus.com/about-aqf/coverage-areahttp://www.asiaqualityfocus.com/about-aqf/contact-ushttp://www.asiaqualityfocus.com/useful-corner/product-inspection-standardshttp://www.asiaqualityfocus.com/useful-corner/product-inspection-standardshttp://www.asiaqualityfocus.com/inspection-serviceshttp://www.asiaqualityfocus.com/factory-auditshttp://www.asiaqualityfocus.com/about-aqf/coverage-area -
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How much does it cost?
roduct Inspections and )actory udits start at 72&8 all inclusive. roduct inspections are usually
perormed within 2 man=day.
The number o man=days needed depends on the total ordered %uantity, the comple+ity o your
product and the number o reerences to inspect. );I, while boo/ing your product inspection online,
you will get a %uotation beore conrming your order.
"ead more about the man=day calculationand chec/ ourprice conditions
How can I pay?
;ou will recei#e one in#oice at the end o the month with all the inspections we perormed on your
behal. This in#oice is payable upon receipt by TT or ayal. We in#oice in F$A but you can pay us in
any major currency.
Do you offer any discounts?
We ofer special pac/ages or our 1I clients who boo/ regular inspections and ha#e been wor/ing with
us or an e+tended period o time.
What happens if non-conforming goods are found when
the shipment arrives?
It is e+tremely rare that non=conorming goods ma/e it out o the actory i () is hired. In the #ast
majority o cases, the root cause turns out to be damage during shipping or shipments were appro#ed
ater a ailed inspection and the buyer trusts the actory 5who was li/ely supposed to rewor/ the
goods9 enough to ship without ha#ing perormed a re=inspection or a deect sorting ser#ice. Thereore,
we highly recommend you to boo/ re=inspection or deect sorting ser#ice ater a ailed inspection and
to wor/ with your shipping partners to insure the product against damage in transit. () guarantees
that we will inspect the product to the standard and methods appro#ed by the client 5including chosen
sampling si&e9. In the e#ent that our inspectors do not ollow the agreed standards, () will ma/e a
reund o up to times the price o the inspection.
http://www.asiaqualityfocus.com/blog/relation-between-man-days-calculation-and-aql-table/http://www.asiaqualityfocus.com/about-aqf/our-fees-and-pricinghttp://www.asiaqualityfocus.com/about-aqf/our-fees-and-pricinghttp://www.asiaqualityfocus.com/blog/relation-between-man-days-calculation-and-aql-table/http://www.asiaqualityfocus.com/about-aqf/our-fees-and-pricing -
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Why doesn't AQF provide a warranty on behalf of the
supplier?
s it is not economically #iable or most clients to inspect e#ery unit in the order,(Etables determine
the number o units to be inspected which will yield a statistically reliable sample si&e. In other words,
i the inspection on the randomly selected lot goes well, then it is statistically unli/ely that deects will
be ound in the rest o the order. )or e+ample, i there are 233 master cartons in an order and 3 units
per master carton or 333 units total. ur inspectors would open at random a select set o master
cartons 5the s%uare root o the total number o cartons9 and urther select at random a set o indi#idual
units inside that master carton as per sampling si&e chosen by the client. 'owe#er, i the supplier
/new they had a ew do&en deects and pac/aged the deects all together in one section o one master
carton, then it would be statistically unli/ely that our inspector would nd this poc/et o deects. )or
this reason, () does not pro#ide a warranty on behal o the supplier. But we stress to our clients that
they should ha#e robust s, warranty terms and payment terms with their suppliers that protects
their interests. Gegotiating such terms with the supplier is outside o the scope o our business at (),
but our Dndorsed artners can help with the negotiations and contract re#iew.
Where do I send golden / reference / pre-production /
approval samples?
It is best to send them directly to your actory, in a sealed pac/age to our attention. In 0hina, you can
also send samples to our oHce, where we will seal them and send them to the actory to the attention
o our inspector. () will absorb courier ees up to F$A. 'elp us identiy the pac/age by writing the
() order number on it. 1eriy which oHce to send it to by chec/ing our oHceCs address on your
dashboard or contact your account manager directly.
How can I get production samples collected during an
inspection?
Eet us /now that you would li/e us to collect production samples. This can be done either online or by
contacting your account manager. We can pic/ normal samples at random or select deecti#e
samples or your reerence. This ser#ice is ree o charge and samples are sent to you using your
courier account. lternati#ely, we can send the samples to you or to our oHce and you co#er any
courier ees e+ceeding F$A.
We can also pic/ up production samples without perorming an inspection. The cost is roughly 2!7 man=
day.
lease contact uswith any urther %uestions.
http://www.asiaqualityfocus.com/useful-corner/product-inspection-standardshttp://www.asiaqualityfocus.com/useful-corner/product-inspection-standardsmailto:[email protected]?subject=Information%20about%20your%20serviceshttp://www.asiaqualityfocus.com/useful-corner/product-inspection-standardsmailto:[email protected]?subject=Information%20about%20your%20services -
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Quality control terms and glossary
A
cceptance Gumber cceptance $ampling
ppro#al $ample
(E
B
Batch!Eot!$ampling
C
0ontainer Eoading Inspection 50EI9
0ontinuous $ampling lan
0ost o oor (uality
0ost o (uality
D
Aeects and Aeecti#es
Aeects per 'undred Fnits
Aouble $ampling lan Arawing o $amples
Auring roduction Inspection 5AI9
E
D+pression o Gonconormance
F
)actory udit
)irst=rticles Inspection
I
Inspection
http://www.asiaqualityfocus.com/useful-corner/glossary#acceptance-numberhttp://www.asiaqualityfocus.com/useful-corner/glossary#acceptance-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#approval-samplehttp://www.asiaqualityfocus.com/useful-corner/glossary#aqlhttp://www.asiaqualityfocus.com/useful-corner/glossary#batch-lot-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#container-loading-inspection-clihttp://www.asiaqualityfocus.com/useful-corner/glossary#continuous-sampling-planhttp://www.asiaqualityfocus.com/useful-corner/glossary#cost-of-poor-qualityhttp://www.asiaqualityfocus.com/useful-corner/glossary#cost-of-qualityhttp://www.asiaqualityfocus.com/useful-corner/glossary#defects-and-defectiveshttp://www.asiaqualityfocus.com/useful-corner/glossary#defects-per-hundred-unitshttp://www.asiaqualityfocus.com/useful-corner/glossary#double-sampling-planhttp://www.asiaqualityfocus.com/useful-corner/glossary#drawing-of-sampleshttp://www.asiaqualityfocus.com/useful-corner/glossary#during-production-inspection-dpihttp://www.asiaqualityfocus.com/useful-corner/glossary#expression-of-nonconformancehttp://www.asiaqualityfocus.com/useful-corner/glossary#factory-audithttp://www.asiaqualityfocus.com/useful-corner/glossary#first-articles-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#acceptance-numberhttp://www.asiaqualityfocus.com/useful-corner/glossary#acceptance-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#approval-samplehttp://www.asiaqualityfocus.com/useful-corner/glossary#aqlhttp://www.asiaqualityfocus.com/useful-corner/glossary#batch-lot-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#container-loading-inspection-clihttp://www.asiaqualityfocus.com/useful-corner/glossary#continuous-sampling-planhttp://www.asiaqualityfocus.com/useful-corner/glossary#cost-of-poor-qualityhttp://www.asiaqualityfocus.com/useful-corner/glossary#cost-of-qualityhttp://www.asiaqualityfocus.com/useful-corner/glossary#defects-and-defectiveshttp://www.asiaqualityfocus.com/useful-corner/glossary#defects-per-hundred-unitshttp://www.asiaqualityfocus.com/useful-corner/glossary#double-sampling-planhttp://www.asiaqualityfocus.com/useful-corner/glossary#drawing-of-sampleshttp://www.asiaqualityfocus.com/useful-corner/glossary#during-production-inspection-dpihttp://www.asiaqualityfocus.com/useful-corner/glossary#expression-of-nonconformancehttp://www.asiaqualityfocus.com/useful-corner/glossary#factory-audithttp://www.asiaqualityfocus.com/useful-corner/glossary#first-articles-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection -
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Inspection by ttribute
Inspection 0hec/ Eist
Inspection Ee#els
Inspection rotocol
I$
L
Eot or Batch
N
Gonconormance
Gormal Inspection
P
ercent Aeecti#e
re $hipment Inspection 5$I9
R
"andom $ampling
"educed Inspection
"ejection Gumber
"epresentati#e $ampling
"esubmitted Eots or Batches
S
$-333
$ample
$ampling lans
$e#erity o Inspection
$ingle $ample lan
T
Tightened Inspection
U
http://www.asiaqualityfocus.com/useful-corner/glossary#inspection-by-attributehttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-checklisthttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-levelshttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-protocolhttp://www.asiaqualityfocus.com/useful-corner/glossary#isohttp://www.asiaqualityfocus.com/useful-corner/glossary#lot-or-batchhttp://www.asiaqualityfocus.com/useful-corner/glossary#nonconformancehttp://www.asiaqualityfocus.com/useful-corner/glossary#normal-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#percent-defectivehttp://www.asiaqualityfocus.com/useful-corner/glossary#pre-shipment-inspection-psihttp://www.asiaqualityfocus.com/useful-corner/glossary#random-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#reduced-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#rejection-numberhttp://www.asiaqualityfocus.com/useful-corner/glossary#representative-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#resubmitted-lots-or-batcheshttp://www.asiaqualityfocus.com/useful-corner/glossary#sa8000http://www.asiaqualityfocus.com/useful-corner/glossary#samplehttp://www.asiaqualityfocus.com/useful-corner/glossary#sampling-planshttp://www.asiaqualityfocus.com/useful-corner/glossary#severity-of-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#single-sample-planhttp://www.asiaqualityfocus.com/useful-corner/glossary#tightened-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-by-attributehttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-checklisthttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-levelshttp://www.asiaqualityfocus.com/useful-corner/glossary#inspection-protocolhttp://www.asiaqualityfocus.com/useful-corner/glossary#isohttp://www.asiaqualityfocus.com/useful-corner/glossary#lot-or-batchhttp://www.asiaqualityfocus.com/useful-corner/glossary#nonconformancehttp://www.asiaqualityfocus.com/useful-corner/glossary#normal-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#percent-defectivehttp://www.asiaqualityfocus.com/useful-corner/glossary#pre-shipment-inspection-psihttp://www.asiaqualityfocus.com/useful-corner/glossary#random-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#reduced-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#rejection-numberhttp://www.asiaqualityfocus.com/useful-corner/glossary#representative-samplinghttp://www.asiaqualityfocus.com/useful-corner/glossary#resubmitted-lots-or-batcheshttp://www.asiaqualityfocus.com/useful-corner/glossary#sa8000http://www.asiaqualityfocus.com/useful-corner/glossary#samplehttp://www.asiaqualityfocus.com/useful-corner/glossary#sampling-planshttp://www.asiaqualityfocus.com/useful-corner/glossary#severity-of-inspectionhttp://www.asiaqualityfocus.com/useful-corner/glossary#single-sample-planhttp://www.asiaqualityfocus.com/useful-corner/glossary#tightened-inspection -
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Fnit o roduction
Acceptance Number
The acceptance number is the ma+imum number o deects or deecti#e units in the sample that will
permit acceptance lot or batch.
Acceptance Sampling
cceptance $ampling is used to decide whether to accept or reject a production lot. ter selecting a
sampling rom a production lot, we inspect the units, we count how many deects are ound among this
sampling and we use the result 5number o deects ound #ersus ma+imum number o deects allowed9
to decide whether or not to accept or reject the lot.
Approval sample
The appro#al sample, also called golden sample, pre=production sample or =sample, is usually sent
by the buyer to the third party inspection company and manuacturer. It is the product o reerence
and will be compared to the production samples. The production and the appro#al sample should be
#ery similar. n inspection report will point out the diferences.
"ead moreabout the role o the appro#al sample during an inspection.
AQL
The (E has two diferent denitions due to standard changes.
Acceptable Quality Level / MIL-STD-105E / ISO 2859-1 (1999)
Theacceptable le#el 5(E9is dened as the ma+imum percent deecti#e 5or the ma+imum number o
deects per hundred units9 that, or purpose o sampling inspection, can be considered satisactory as
a process a#erage. The sampling plans most re%uently used by the department o Aeense are based
on the (E.
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Acceptance Quality Limit / ANSI/ASQC Z1.4-2003
The (E is the %uality le#el that is the worst tolerable process a#erage when a continuing series o lots
is submitted or acceptance sampling. The ollowing note on the meaning o (E was introduced with
the G$I!$( J2.=733* re#ision:
The concept of AQL onl applies !hen an acceptance sa"pling sche"e !ith rules for s!itching
#et!een nor"al$ tightened and reduced inspection and discontinuance of sa"pling inspection is used%
These rules are designed to encourage suppliers to ha#e process a#erages consistently better than the
(E. I suppliers ail to do so, there is a high probability o being switched rom normal inspection to
tightened inspection where lot acceptance becomes more diHcult.
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nce on tightened inspection, unless correcti#e action is ta/en to impro#e product %uality, it is #ery
li/ely that the rule re%uiring discontinuance o sampling inspection will be in#o/ed. lthough indi#idual
lots with %uality as bad as the (E can be accepted with airly high probability, the designation o an
(E does not suggest that this is necessarily a desirable %uality le#el.
The (E is a parameter o the sampling scheme and should not be conused with a process a#erage
which describes the operating le#el o a manuacturing process. It is e+pected that the product %uality
le#el will be less than the (E to a#oid e+cessi#e non accepted lots. The (E #alues are dened as
percent nonconorming or deects or nonconormities per hundred units.
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Aownloadthe (E table, and read more to get amiliar with the (E table:
Theconditionsto use the (E table.
The (E table history, denition and role.
The relation betweenman=day calculation and (E table.
Batch/Lot/Sampling
batch or lot is a collection o products, all identical in si&e, type, conditions and time o production.
Container Loading Inspection (CLI)
This inspection is perormed at the manuacturerKs warehouse or at the orwarderKs premises. The aim
o this inspection is to #eriy your products, the %uantity and the loading process.
This inspection includes:
an inspection o the container beore the loading 5container condition9
an inspection o your products 5product chec/ according to your !: %uantity, appearance and
general %uality9
an inspection o the loading process 5cartons conditions, lling=up le#el etc9
Continuous Sampling Plan
This is an approach to sampling that is appropriate or the output o processes that deli#er a
continuous Low o a product. In this plan, we start inspecting 233 M o the units coming rom the
process. ter a certain number o items that ha#e been inspected with no deects, the plan goes toinspecting only a raction o items. This continues until we nd a nonconorming unit. t that point, the
plan re#erts bac/ to 233 M inspection ollowing the same pattern.
Cost of Poor Quality
These are the e+tra e+penses caused by deli#ering poor %uality goods to customers. These e+penses
ha#e two sources: internal ailure costs 5rom deects beore customers get the product9 and e+ternal
ailure costs 5costs ater a customer recei#es the poor product or ser#ice9. Aeect sorting, "ewor/,
repairs, image damage, brand damage, client condence lost are a ew e+amples o costs associated
with poor %uality.
Cost of Quality
This reers to all costs in#ol#ed in the pre#ention o %uality issues, deects, assessments o process
perormance, and measurement o nancial conse%uences. 0ost o %uality is the cost justication o
%uality eforts. 0ost o %uality should be seen as an in#estment more than a cost.
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Defects and Defectives
deect is any nonconormance o the unit o product with the specied re%uirements. deecti#e is a
unit o product which contains one or more deects. )ailure to meet re%uirements with respect to
%uality characteristics are usually described in terms o deects or deecti#es.
ritical eect= critical deect is on that judgment and e+perience indicate is li/ely to result in
ha&ardous or unsae conditions or indi#iduals using, maintaining, or depending upon the products6 or
pre#ent perormance o the tactical unction o a major end item. critical deecti#e is a unit o
product that contains one or more critical deects. ;ou can pro#ide your own list o 0ritical Aeects to
be inspected. sia (uality )ocusK deault 0ritical Aeect (E is 3.
+aor eect= major deect is one, other than critical, that is li/ely to result in ailure, or to reduce
materially the usability o the unit o product or its intended purpose. major deecti#e is a unit o
product that contains one or more major deects. ;ou can pro#ide your own list o @ajor Aeects to be
inspected. sia (uality )ocusK deault @ajor Aeect (E is 7..
+inor eect= minor deect is one that is not li/ely to reduce materially the usability o the unit o
product or its intended purpose, or is a departure rom established standards ha#ing little bearing on
the efecti#e use or operation o the unit o product. @inor deecti#e is a unit o product that contains
one or more deects. ;ou can pro#ide your own list o @inor Aeects to be inspected. sia (uality
)ocusK deault @inor Aeect (E is .3.
"ead more about@ajor, @inor and 0ritical deectto easily diferentiate them.
Defects per Hundred Units
The number o deects per hundred units o any gi#en %uantity units o product is one hundred timesthe number o deects contained therein 5one or more deects being possible in any unit o product9
di#ided by the total number o units o product, i.e.: 5Gumber o deecti#es + 2339 ! 5number o units
inspected9
Double Sampling Plan
This is an inspection techni%ue in which you inspect a rst lot o n2 si&e, which leads you either to
accept or reject it. I you reject it, then we inspect a second sample o a larger lot si&e n7, which in turn
leads to a decision to accept or reject the lot.
Drawing of Samples
Basic to sampling inspection is the assurance that the sample selected rom a %uantity o units
represents the %uality o that %uantity o units. 'ence, the procedure used to select units rom a lot
must be such that it assures a sample ree o bias
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During Production Inspection (DPI)
The inspection ta/es place when about 73M to 3M o the production has been completed. The aim is
to ensure that contractual obligations regarding specications, pac/aging, pac/ing and mar/ing are
met and to chec/ i the actory will be able to respect the production schedule. I recommendations
ha#e been gi#en during a )irst=rticles Inspection 5)I9, the Auring roduction Inspection determineswhether or not these correcti#e action plan has been successully implemented.
Expression of Nonconformance
The e+tent o nonconormance o product shall be e+pressed either in terms o percent deecti#e or in
terms o deects per hundred units 5A'F9.
Factory Audit
This is a ull e#aluation o your supplier according to the I$ standards. It co#ers: prole o the
supplier, internal organi&ation, saety regulations, %uality processes, perormance, deli#ery terms and"
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Inspection by Attribute
Inspection by attributes is inspection where by either the unit o product is classied simply as
deecti#e or non=deecti#e, or the number o deects in the unit o product is counted, with respect to a
gi#en re%uirement or set o re%uirements.
Inspection checklist
It is a document in which are listed all the details an inspector should chec/ during an inspection. The
objecti#e is to a#oid missing any o them.
"ead moreabout how useul is the inspection chec/list or an importer.
Inspection Levels
The standards pro#ides or three general inspection le#els and our special inspection le#els. These
se#en le#els permit the user to balance the cost o inspection against the amount o protection
re%uired.
"ead more and get amiliar with the inspection le#els:
The diference between the general and special inspection le#elo the (E table by
reading this article. 'ow to choose the right (E inspection le#el.
Inspection protocol
It denes all the process and steps the (0 has to ollow in order to perorm the inspection. It includes
the list o the details to chec/ and the order specication #erication.
ISO
I$ is a networ/ o the national standards institutes o 28 countries, on the basis o one member per
country, with a 0entral $ecretariat in Nene#a, $wit&erland, that coordinates the system. I$ is a non=
go#ernmental organi&ation: its members are not, as is the case in the Fnited Gations system,
delegations o national go#ernments. Ge#ertheless, I$ occupies a special position between the public
and pri#ate sectors. This is because, on the one hand, many o its member institutes are part o the
go#ernmental structure o their countries, or are mandated by their go#ernment. n the other hand,
other members ha#e their roots uni%uely in the pri#ate sector, ha#ing been set up by national
partnerships o industry associations.
I$ ?333 $tandards: this is a set o %uality standards de#eloped in 2?-8 by the International
rgani&ation or $tandardi&ation. The three major areas o certication are as ollows:
I$ ?337: co#ers e#erything e+cept design and de#elopment.
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I$ ?332: co#ers all the processes o a company rom design and de#elopment to procurement,
production, testing, installation and ser#ice.
I$ ?33*: co#ers only inspection and testing.
Lot or Batch
The lot si&e is the total number o units a#ailable or random sampling. The lot si&e only includes
pac/ed products. lso called inspection lot or inspection batch, it is a collection o units o product
rom which a sample is to drawn and inspected to determine conormance with the acceptance
criteria.
Nonconformance
Gonconormance may be dened as the ailure o a unit o product to conorm to specied
re%uirements or any stated %uality characteristic. The e+tent o nonconormance o product to the
re%uired %uality characteristics shall be e+pressed either in terms o percent deecti#e or in terms odeects per hundred units 5A'F9.
Normal Inspection
Gormal inspection is what is used where there is no e#idence that the %uality o product being
submitted is better or worse than the specied %uality le#el.
Percent Defective
The percent deecti#e o any gi#en %uantity o units o product is one hundred times the number o
deecti#e units o product contained therein di#ided by the total number o units o product, i.e.:
ercent deecti#e O number o deecti#es +233 ! number o units inspected.
Pre Shipment Inspection (PSI)
lso called )inal "andom Inspection 5)"I9, it is the most common inspection and it is perormed when
233M o the goods ordered are nished, and at least -3M o the goods are pac/ed into e+port cartons.
$amples are selected randomly, according to sampling standards 5usually (E table9 and procedures.
They will be inspected according to your specications, re%uirements and according to our protocols
and e+pertise.
This inspection ensures that the production is in accordance with the specications, purchase orders or
letters o credit. It co#ers: product appearance 5(E9, wor/manship %uality, si&e measurements, weight
chec/, unctionality assortment, accessories, labeling < logos, pac/aging, pac/ing and other tests and
special re%uirements, depending on the product and the e+port mar/et.
"ead about the role o the purchase orderor sourcing in 0hina more securely.
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Random Sampling
This is a standard sampling method by which random samples o units are chosen such that all
combinations o these units ha#e an e%ual chance o being chosen as the sample.
Reduced Inspection
"educed inspection under a sampling plan uses the same %uality le#el as or normal inspection, but
re%uires a smaller sample or inspection.
Rejection Number
The rejection number is the minimum number o deects or deecti#e units in the sample that will
cause rejection o the lot represented by the sample.
Representative Sampling
When appropriate, the number o units in the sample shall be selected in proportion to the si&e o sub=
lots or sub=batches, or parts or the lot or batch, identied by some rational criterion. When
representati#e sampling is used, the units rom each part o the lot or batch shall be selected at
random.
Resubmitted Lots or Batches
Eots or batches ound unacceptable shall be resubmitted or re=inspection only ater all units are re=
e+amined or retested and all deecti#e units are remo#ed or deects corrected. The responsible
authority shall determine whether normal or tightened inspection shall be used and whether re=
inspection shall include all types or classes o deects or only the particular types or classes o deects
which caused initial rejection.
Sample
sample consists o one or more units o product drawn rom a lot or batch, the units o the sample
being selected at random without regard to their %uality. The number o product in the sample is the
sample si&e.
Sampling Plans
lot sampling plan is a statement o the sample si&e or si&es to be used and the associated
acceptance and rejection numbers.
Severity of Inspection
The se#erity o inspection concerns the total amount, /ind and e+tent o inspection specied by the
%uality assurance pro#isions established or the unit o product, or as dictated by %uality history.
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Single Sample Plan
single sampling plan is a type o sampling plan by which the results o a single sample rom an
inspection lot are conclusi#e in determining acceptability. The number o sample units inspected shall
be e%ual to the sample si&e gi#en by the plan.
Tightened Inspection
Tightened inspection under a sampling procedure plan uses the %uality le#el as or normal inspection,
but re%uires more stringent acceptance criteria.
Unit of Production
The unit o product is the thing inspected in order to determine its classication as deecti#e or non=
deecti#e or to count the number o deects. It may be a single article, a pair, a set, a length, an area,
an operation, a #olume, a component o an end product, or the end product itsel. The unit o product
may or may not be the same as the unit o purchase, supply, production, or shipment.
International quality standards
for product inspections
How are AQF product inspections performed?
sia 9ualit /ocusperorms product inspections ser#icesaccording to:
"ecogni&ed international :ualit stanar or prouct inspections%I$ 7-?=2
5G$I!$(0 J2.=733*9, also /nown as the (E Tables, unless another standard is re%uested by the
client. 0lientKs re:uire'ents$specications, criteria and instructions.
() teamKs epertise andeperience in %uality control.
() Western co''on sense6
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What do we inspect during an inspection? The %uantity produced 5semi nished, nished and pac/ed9
The #isual appearance 5cosmetic chec/ o the mass production9
The product specications 5si&e, dimensions, colors9
The labeling and mar/ing
The pac/ing and pac/aging
ll possible unctions and possible tests 5saety, abuse, printing, etc.9
What quality standards do we use for inspections?
Based on the sampling si&e chosenrom the (E tables= highly recognised international %uality
standards or product inspections = we careully ensure to select production samples randomly. We
inspect the samples and classiy the deects into critical, major and minor deects. We use detailed
chec/ lists or these denitions = our clients are in#ited to ma/e amendments.
ccording to the number o deects ound or each type and according to the number o deects
allowed 5gures gi#en by the (E tables9, we will ad#ise you to acceptor to reectyour shipment.
Then it is up to you to ma/e your own decision based on the inormation and recommendations we
ha#e pro#ided to you. We suggest that you discuss the ndings with your #endor and the manuacturer
and you as/ him to pay attention!rewor/!re=produce!sort out the products.
How to use the AQL Tables?
The (E tables belong to international %uality standards or product inspections. They will help to
determine the sampling si&e we will need to inspect according to your ordered %uantity and your le#el
o se#erity 5I, II or III9. The standard le#el, the one used by deault and by ?-M o the people is
the level II or a stanar inspection. I your order has multiple reerences, ideally we should at
least inspect a le#el II on each reerence.
Indeed, or a standard order, the standard le#el II rom the (E gi#es the minimum sampling si&e we
should chec/ per reerence i we do not want to ta/e additional ris/s. I we inspect a general le#el II
sampling si&e on a multiple reerences orders, then the sampling si&e is diluted and di#ided by thenumber o reerences, increasing the ris/s as the sa'pling si.e 'ust be representative enoug.
@ore inormation about:
'ow touse the (E table
0hoosing the right (E inspection le#el
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How to find your sampling size on the AQL table?
In order to nd the necessary sampling si&e to be inspected, we loo/ at the rst chart and nd on the
let side the range o items being produced in total. ;ou ha#e the choice o le#els I, II and III, with Ee#el
III being the most stringent testing and le#el I being the least. Ee#el II is the standard and is most oten
used. )or e+ample, i you are producing -333 items, at le#el II you ha#e the letter E, which in the
second table says to inspect 733 items.
n the top o the second chart are the deect le#els, ranging rom 3 to P.. ;ou can choose which le#el
to apply or your type o deect: critical, major and minor. Fsually most importers will choose standard
deect le#els which are 3!7.! but one can choose 2!2!2 i he wishes or 3!2.!7. li/e in the
automoti#e industry. Fsing the standard 3!7.! deect le#els and a sample si&e o 733, we see that i
you ha#e more than 3 critical deects, 23 major deects or 2 minor deects, you should reject your
shipment. course the decision about what to do ater your recei#ed the inspection results belongs to
you. @ost importers will wish to discuss all inspection ndings with their #endor!manuacturer in order
to impro#e whate#er possible. In case the inspection results are #ery close to (E limits, it is important
that you double chec/ i the le#el o ound deects is acceptable to you or not.
Aownload the (E table.
http://www.asiaqualityfocus.com/uploads/media/1402039401_aqf-aql-table-iso-2859-ansi-asqc-z1-4.pdfhttp://www.asiaqualityfocus.com/uploads/media/1402039401_aqf-aql-table-iso-2859-ansi-asqc-z1-4.pdf -
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Inspection TypesIto assure understanding o your product < order
)Ior a successul transition to mass production
AIto impro#e %uality during mass production
$Ito detect and sol#e problems beore shipment
0E$ to ensure punctual < sae transport
A$$to sort out all the most important deects
@to continuously understand and impro#e processes
Product ExpertiseTe+tiles < pparel
Toys
)urniture < 'omeware
Dlectronics < Dlectrical
Eu+ury roducts
romotional Noods < Nits
utomoti#e Industry
http://www.asiaqualityfocus.com/inspection-serviceshttp://www.asiaqualityfocus.com/inspection-services/pre-production-inspectionhttp://www.asiaqualityfocus.com/inspection-services/first-article-inspectionhttp://www.asiaqualityfocus.com/inspection-services/during-production-inspectionhttp://www.asiaqualityfocus.com/inspection-services/pre-shipment-inspectionhttp://www.asiaqualityfocus.com/inspection-services/container-loading-supervisionhttp://www.asiaqualityfocus.com/inspection-services/defect-sorting-servicehttp://www.asiaqualityfocus.com/inspection-services/defect-sorting-servicehttp://www.asiaqualityfocus.com/inspection-services/production-monitoringhttp://www.asiaqualityfocus.com/inspection-services/production-monitoringhttp://www.asiaqualityfocus.com/about-aqf/expertisehttp://www.asiaqualityfocus.com/about-aqf/expertise/apparel-textiles-inspectionshttp://www.asiaqualityfocus.com/about-aqf/expertise/toys-inspectionshttp://www.asiaqualityfocus.com/about-aqf/expertise/home-goods-furniture-inspectionshttp://www.asiaqualityfocus.com/about-aqf/exper