perform qc process

8/3/2019 Perform Qc Process

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By :-

NOR ARNIZA BINTI JAMIL

VOCATIONAL TRAINING OFFICER, J41

PERFORM QUALITY

CONTROL PROCESS

1 MALAYSIA TRAINING PROGRAM

7 QC TOOLS
http://www.pdfcomplete.com/cms/hppl/tabid/108/Default.aspx?r=q8b3uige22


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5. Check Sheet

Check sheets help organize data by category.

They show how many times each particular valueoccurs, and their information is increasingly helpfulas more data are collected.

Main applications of a check sheet includeregistering how often different problems occur andregistering the frequency of incidents that arebelieved to cause problems.


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Advantages of using a check sheet

Effective way of displaying data

Easy to useCan identify the root cause of a problemA first step in the construction of other graphical toolsProvides a structure for uniform data collectionCan be used to substantiate or refute allegations


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How to construct a check sheet

1. Clearly define what events (problem or process) are to be recorded.(Add a category of other to capture incidents not easily categorized

into any of the specified groups.

2. Define the period for data recording and suitable intervals. The timeperiod should be representative (that is, a one day sample onMonday may not be representative of a typical day).

3. Design the check sheet to be used during data recording, allocatingspace for recording, and for summarizing within the intervals and theentire recording period.


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How To Construct A Check Sheet Cont..

4. Develop a check sheet that is easy to understand. All columnsshould be clearly labeled.

5. Perform the data collection during the agreed period, ensuringthat everyone understands the tasks and the events to berecorded.

6. Analyze the data to identify events with unusually high or lowoccurrences.

7. Train all those involved on gathering data. A uniform datacollection technique is vital.

8. Plot the information on a check sheet.


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An example of the use of a check sheet

(taken from Root Cause Analysis)

A book store located in a large shopping mall consistently achieved lower salesper day than budgeted. The staff noted that quite a few customers came intothe store to browse, but left without buying anything. When considering this

problem (not tapping the customer base potential there), a wide range ofpossible causes surfaced including:

The customers did not find what they were looking for.The staff did not offer the necessary help.Sought items were temporarily sold out.Sought items were not carried by the store.

Prices were too high.There was too long a line at the checkout counter.Certain types of credit cards were not accepted.Lighting was poor in some areas of the store.There were no places to sit and look through books before deciding to buy.
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Cont..

The difficultly in identifying the actual problem and how often it occurredmake it difficult for the store personnel to implement any changes.

Thus, during a two-week period, many of the customers leaving withoutmaking purchases were courteously asked why this happened. Theresponses were logged in a check sheet, shown below, and give amuch clearer idea of where to start to improve the situation.


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Result..


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6. SCATTER DIAGRAM

Also called: scatter plot, XY graph

Description

The scatter diagram graphs pairs of numerical data,with one variable on each axis, to look for arelationship between them. If the variables arecorrelated, the points will fall along a line or curve.The better the correlation, the tighter the points will

hug the line.


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When to Use a Scatter Diagram

When you have paired numerical data.When your dependent variable may have multiple values for each

value of your independent variable.When trying to determine whether the two variables are related,such as

o When trying to identify potential root causes of problems.o After brainstorming causes and effects using a fishbone

diagram, to determine objectively whether a particularcause and effect are related.

o When determining whether two effects that appear to berelated both occur with the same cause.

o When testing for autocorrelation before constructing acontrol chart.

5. SCATTER DIAGRAM cont..


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X and Y Data Correlation

Strong Positive Correlation

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Y Series1

Strong Negative Correlation

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Positive Correlation

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Negative Correlation

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No Correlation

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Steps in using a scatter

diagrams

1. Select and define the two variables to be analyzed in the

individual chart.2. Measure the two variables, if data has not already beencollected.

3. The set of data pairs should consist of the at least thirty, butpreferably more like one hundred data pairs.

4. Design the chart by placing the independent variable onthe horizontal axis. The independent variable is the factorbelieved to be governing relationship between the twovariables.


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5. On the vertical axis, insert the dependent variable thatis, the factor believed to change in proportion to the

independent variable.6. Plot the data pairs themselves in the chart area.7. Examine the completed chart, looking for patterns that

indicate a connection between the two variables.8. If correlation patterns are identified, investigate any

third variable involvement before drawing definiteconclusions.

Steps In Using A Scatter

Diagrams cont..


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Scatter Diagrams Example..

Situation:

The new commissioner of the American

Basketball League wants to construct ascatter diagram to find out if there is anyrelationship between a player s weight andher height. How should she go about making

her scatter diagram?

1. Collect the data (Remember to use 30-100 paired samples).


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2. Data Collected..

PLAYER WEIGHT HEIGHT

1 57 156

2 58 114

3 59 132

4 59 147

5 60 157

6 62 145

7 66 1578 67 168

9 68 147

10 68 179

11 68 147

12 68 168

13 68 156

14 69 17515 69 173

16 70 168

17 70 175

18 71 158

19 71 169

20 72 212

PLAYER WEIGHT HEIGHT

21 72 182

22 72 168

23 72 168

24 73 157

25 74 180

26 74 216

27 74 17928 75 194

29 75 184

30 75 167

31 76 168

32 76 225

33 77 200

34 78 18735 78 194

36 79 208

37 79 216

38 80 215

39 81 225

40 84 214


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3. SCATTER DIAGRAM..ans..

100

120

140

160

180

200

220

240

45 50 55 60 65 70 75 80 85 90

PLAYER HEIGHT/WEIGHTHEIGHT, cm

WEIGHT, kg


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4. Interpret your chart

According to this scatter diagram the newcommissioner was right. There does

seem to be a positive correlation between

a player's weight and her height. In other

words, the taller a player is the more shetends to weight.


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ASSIGNMENT..

Collect the data for car age and the price.

Interpret your chart for the relationsbetween the car age and the price.

Collect at least for 50pcs data.


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ADDITIONAL ASSIGNMENT..

REFER HANDOUT..


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7. CONTROL CHART

Description

The control chart is a graph used to study how aprocess changes over time. Data are plotted in time order.

A control chart always has a central line for theaverage, an upper line for the upper control limit and a lowerline for the lower control limit.

These lines are determined from historical data. Bycomparing current data to these lines, you can drawconclusions about whether the process variation is consistent(in control) or is unpredictable (out of control, affected byspecial causes of variation).

Also called: statistical process control


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Control charts for variable data are used in pairs. The top chartmonitors the average, or the centering of the distribution of data from

the process. The bottom chart monitors the range, or the width of thedistribution. If your data were shots in target practice, the average iswhere the shots are clustering, and the range is how tightly they areclustered. Control charts for attribute data are used singly.


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When to Use a Control Chart?

When controlling ongoing processes by finding and correctingproblems as they occur.

When predicting the expected range of outcomes from a

process.When determining whether a process is stable (in statisticalcontrol).

When analyzing patterns of process variation from specialcauses (non-routine events) or common causes (built into theprocess).

When determining whether your quality improvement projectshould aim to prevent specific problems or to make fundamentalchanges to the process.


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Control Chart Basic Procedure

Choose the appropriate control chart for your data.Determine the appropriate time period for collecting

and plotting data.Collect data, construct your chart and analyze the data.Look for out-of-control signals on the control chart.When one is identified, mark it on the chart andinvestigate the cause. Document how you

investigated, what you learned, the cause and how itwas corrected.


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Out-of-control signals

A single point outside the control limits. In Figure 1, pointsixteen is above the UCL (upper control limit).Two out of three successive points are on the same side of thecenterline and farther than 2 from it. In Figure 1, point 4

sends that signal.Four out of five successive points are on the same side of thecenterline and farther than 1 from it. In Figure 1, point11 sends that signal.A run of eight in a row are on the same side of the centerline.Or 10 out of 11, 12 out of 14 or 16 out of 20. In Figure 1,

point 21 is eighth in a row above the centerline.Obvious consistent or persistent patterns that suggestsomething unusual about your data and your process.


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Continue to plot data as they are generated. As each new datapoint is plotted, check for new out-of-control signals.o When you start a new control chart, the process may be

out of control. If so, the control limits calculated from thefirst 20 points are conditional limits. When you have atleast 20 sequential points from a period when the processis operating in control, recalculate control limits


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ASSIGNMENT..

REFER HANDOUT..

perform qc process

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