© 2006 prentice hall, inc.s10 – 1 operations management supplement 10 – work measurement ©...
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© 2006 Prentice Hall, Inc. S10 – 1
Operations ManagementOperations ManagementSupplement 10 – Work MeasurementSupplement 10 – Work Measurement
© 2006 Prentice Hall, Inc.
PowerPoint presentation to accompanyPowerPoint presentation to accompany Heizer/Render Heizer/Render Principles of Operations Management, 6ePrinciples of Operations Management, 6eOperations Management, 8e Operations Management, 8e
© 2006 Prentice Hall, Inc. S10 – 2
OutlineOutline
Labor Standards And Work Labor Standards And Work MeasurementMeasurement
Historical ExperienceHistorical Experience
Time StudiesTime Studies
Predetermined Time Predetermined Time StandardsStandards
Work SamplingWork Sampling
© 2006 Prentice Hall, Inc. S10 – 3
Learning ObjectivesLearning Objectives
When you complete this supplement, When you complete this supplement, you should be able to:you should be able to:
Identify or Define:Identify or Define:
Four ways of establishing labor Four ways of establishing labor standardsstandards
© 2006 Prentice Hall, Inc. S10 – 4
Learning ObjectivesLearning Objectives
When you complete this supplement, When you complete this supplement, you should be able to:you should be able to:
Describe or Explain:Describe or Explain:
Requirements for good labor Requirements for good labor standardsstandards
Time studyTime study
Predetermined time standardsPredetermined time standards
Work samplingWork sampling
© 2006 Prentice Hall, Inc. S10 – 5
Labor Standards and Work Labor Standards and Work MeasurementMeasurement
Started early in the 20th centuryStarted early in the 20th century
Important to both manufacturing Important to both manufacturing and service organizationsand service organizations
Necessary for determining staffing Necessary for determining staffing requirementsrequirements
Important to labor incentive Important to labor incentive systemssystems
© 2006 Prentice Hall, Inc. S10 – 6
Meaningful Standards Help Meaningful Standards Help DetermineDetermine
1.1. Labor content of items producedLabor content of items produced
2.2. Staffing needsStaffing needs
3.3. Cost and time estimatesCost and time estimates
4.4. Crew size and work balanceCrew size and work balance
5.5. Expected productionExpected production
6.6. Basis of wage incentive plansBasis of wage incentive plans
7.7. Efficiency of employeesEfficiency of employees
© 2006 Prentice Hall, Inc. S10 – 7
Labor StandardsLabor Standards
May be set in four ways:May be set in four ways:
1.1. Historical experienceHistorical experience
2.2. Time studiesTime studies
3.3. Predetermined time standardsPredetermined time standards
4.4. Work samplingWork sampling
© 2006 Prentice Hall, Inc. S10 – 8
Historical ExperienceHistorical Experience
How the task was performed last How the task was performed last timetime
Easy and inexpensiveEasy and inexpensive
Data available from production Data available from production records or time cardsrecords or time cards
Data is not objective and may be Data is not objective and may be inaccurateinaccurate
Not recommendedNot recommended
© 2006 Prentice Hall, Inc. S10 – 9
Time StudiesTime Studies
Involves timing a sample of a Involves timing a sample of a worker’s performance and using it worker’s performance and using it to set a standardto set a standard
Requires trained and experienced Requires trained and experienced observersobservers
Cannot be set before the work is Cannot be set before the work is performedperformed
© 2006 Prentice Hall, Inc. S10 – 10
Time StudiesTime Studies
1.1. Define the taskDefine the task
2.2. Divide the task into precise Divide the task into precise elementselements
3.3. Decide how many times to measure Decide how many times to measure the taskthe task
4.4. Time and record element times and Time and record element times and rating of performancerating of performance
© 2006 Prentice Hall, Inc. S10 – 11
Time StudiesTime Studies
5.5. Compute average cycle timeCompute average cycle time
Average Average observed observed cycle timecycle time
sum of the times recorded sum of the times recorded to perform each elementto perform each element
number of cycles observednumber of cycles observed==
6.6. Determine performance rating Determine performance rating and normal timeand normal time
Normal time = xNormal time = xaverage average
observed observed cycle timecycle time
performance performance rating factorrating factor
© 2006 Prentice Hall, Inc. S10 – 12
Time StudiesTime Studies
7.7. Add all the normal times for each Add all the normal times for each element to develop the total normal element to develop the total normal time for the tasktime for the task
8.8. Compute the standard timeCompute the standard time
Standard time =Standard time =total normal timetotal normal time
1 -1 - allowance factor allowance factor
© 2006 Prentice Hall, Inc. S10 – 13
Rest AllowancesRest Allowances
Personal time allowancePersonal time allowance 4% - 7% of total time for use of 4% - 7% of total time for use of
restroom, water fountain, etc.restroom, water fountain, etc.
Delay allowanceDelay allowance Based upon actual delays that occurBased upon actual delays that occur
Fatigue allowanceFatigue allowance Based on our knowledge of human Based on our knowledge of human
energy expenditureenergy expenditure
© 2006 Prentice Hall, Inc. S10 – 14
Rest AllowancesRest Allowances
1.1. Constant allowanceConstant allowance
(A)(A) Personal allowance ……………...Personal allowance ……………...
55
(B)(B) Basic fatigue allowance …………Basic fatigue allowance …………
44
2.2. Variable allowances:Variable allowances:
(A)(A) Standing allowance ………………Standing allowance ………………
22
(B)(B) Abnormal positionAbnormal position
(i)(i) Awkward (bending) …………Awkward (bending) …………
22
(ii)(ii) Very awkward (lying, Very awkward (lying, stretching) ……………………stretching) ……………………
77
Figure S10.1Figure S10.1
© 2006 Prentice Hall, Inc. S10 – 15
Rest AllowancesRest Allowances
(C)(C) Use of force or muscular energy in Use of force or muscular energy in lifting, pulling, pushinglifting, pulling, pushing
Weight lifted (pounds)Weight lifted (pounds)
20 ……………………………………20 ……………………………………
33
40…………………………………….40…………………………………….
99
60…………………………………….60…………………………………….
1717
(D)(D) Bad light:Bad light:
(i)(i) Well below recommended….Well below recommended….
22
(ii)(ii) Quite inadequate…………….Quite inadequate…………….
55
Figure S10.1Figure S10.1
© 2006 Prentice Hall, Inc. S10 – 16
Rest AllowancesRest Allowances
(E)(E) Atmospheric conditions Atmospheric conditions (heat and humidity) ……………(heat and humidity) ……………
0-100-10
(F)(F) Close attention:Close attention:
(i) Fine or exacting………………..(i) Fine or exacting………………..
22
(ii) Very fine or very exacting……(ii) Very fine or very exacting……
55
(G)(G) Noise level:Noise level:
(i) Intermittent—loud……………..(i) Intermittent—loud……………..
22
(ii) Intermittent—very loud(ii) Intermittent—very loud or high-pitched………………... or high-pitched………………...
55
Figure S10.1Figure S10.1
© 2006 Prentice Hall, Inc. S10 – 17
Rest AllowancesRest Allowances
(H)(H) Mental strain:Mental strain:
(i) Complex or wide span (i) Complex or wide span of attention.…………………….. of attention.……………………..
44
(ii) Very complex…………………..(ii) Very complex…………………..
88
(I)(I) Tediousness:Tediousness:
(i) Tedious…………..………………(i) Tedious…………..………………
22
(ii) Very tedious.……………………(ii) Very tedious.……………………
55
Figure S10.1Figure S10.1
© 2006 Prentice Hall, Inc. S10 – 18
Time Study Example S1Time Study Example S1
Average observed time Average observed time = 4.0= 4.0 minutes minutesWorker rating Worker rating = 85%= 85%Allowance factor Allowance factor = 13%= 13%
Normal time = (average observed time) x (rating factor)Normal time = (average observed time) x (rating factor)
= (4.0)(.85)= (4.0)(.85)
= 3.4= 3.4 minutes minutes
Standard time = = =Standard time = = =normal timenormal time1 -1 - allowance factor allowance factor
3.43.41 - .131 - .13
3.43.4.87.87
= 3.9= 3.9 minutes minutes
© 2006 Prentice Hall, Inc. S10 – 19
Time Study Example S2Time Study Example S2
Allowance factor Allowance factor = 15%= 15%
PerformancePerformanceJob ElementJob Element 11 22 33 44 55 RatingRating
(A)(A) Compose and type letterCompose and type letter 88 1010 9 9 21*21* 1111120%120%
(B)(B) Type envelope addressType envelope address 22 33 2 2 1 1 33105%105%
(C)(C) Stuff, stamp, seal, andStuff, stamp, seal, and 22 11 5*5* 2 2 11110%110%
sort envelopes sort envelopes
Cycle Observed (in minutes)Cycle Observed (in minutes)
1.1. Delete unusual or nonrecurring observations (marked with *)Delete unusual or nonrecurring observations (marked with *)2.2. Compute average cycle times for each elementCompute average cycle times for each element
Average time for A Average time for A = (8 + 10 + 9 + 11)/4 = 9.5= (8 + 10 + 9 + 11)/4 = 9.5 minutes minutesAverage time for B Average time for B = (2 + 3 + 2 + 1 + 3)/5 = 2.2= (2 + 3 + 2 + 1 + 3)/5 = 2.2 minutes minutesAverage time for C Average time for C = (2 + 1 + 2 + 1)/4 = 1.5= (2 + 1 + 2 + 1)/4 = 1.5 minutes minutes
© 2006 Prentice Hall, Inc. S10 – 20
Time Study Example S2Time Study Example S2
3.3. Compute the normal time for each elementCompute the normal time for each element
Normal time for A Normal time for A = (9.5)(1.2) = 11.4= (9.5)(1.2) = 11.4 minutes minutesNormal time for B Normal time for B = (2.2)(1.05) = 2.31= (2.2)(1.05) = 2.31 minutes minutesNormal time for C Normal time for C = (1.5)(1.10) = 1.65= (1.5)(1.10) = 1.65 minutes minutes
Normal time = (average observed time) x (rating)Normal time = (average observed time) x (rating)
4.4. Add the normal times to find the total normal timeAdd the normal times to find the total normal time
Total normal time Total normal time = 11.40 + 2.31 + 1.65 = 15.36= 11.40 + 2.31 + 1.65 = 15.36 minutes minutes
© 2006 Prentice Hall, Inc. S10 – 21
Time Study Example S2Time Study Example S2
5.5. Compute the standard time for the jobCompute the standard time for the job
Standard time =Standard time =total normal timetotal normal time
1 -1 - allowance factor allowance factor
= = 18.07= = 18.07 minutes minutes15.3615.361 - .151 - .15
© 2006 Prentice Hall, Inc. S10 – 22
Determine Sample SizeDetermine Sample Size
How accurate we want to beHow accurate we want to be
The desired level of confidenceThe desired level of confidence
How much variation exists within How much variation exists within the job elementsthe job elements
© 2006 Prentice Hall, Inc. S10 – 23
Determine Sample SizeDetermine Sample Size
Required sample size = n = Required sample size = n = 22
zszshxhx
wherewhere hh == accuracy level desired in accuracy level desired in percent of the job element expressed as percent of the job element expressed as a decimala decimal
zz == number of standard number of standard deviations required for the desired level deviations required for the desired level of confidenceof confidence
ss == standard deviation of the standard deviation of the initial sampleinitial sample
xx == mean of the initial samplemean of the initial sample
nn == required sample sizerequired sample size
© 2006 Prentice Hall, Inc. S10 – 24
Determine Sample SizeDetermine Sample Size
Required sample size = n = Required sample size = n = 22
zszshxhx
wherewhere hh == accuracy level desired in accuracy level desired in percent of the job element expressed as percent of the job element expressed as a decimala decimal
zz == number of standard number of standard deviations required for the desired level deviations required for the desired level of confidenceof confidence
ss == standard deviation of the standard deviation of the initial sampleinitial sample
xx == mean of the initial samplemean of the initial sample
nn == required sample sizerequired sample size
Desired Confidence
(%)
z Value (standard deviation required for
desired level of confidence)
90.0 1.65
95.0 1.96
95.45 2.00
99.0 2.58
99.73 3.00
Common z Values
Table S10.1
© 2006 Prentice Hall, Inc. S10 – 25
Time Study Example S3Time Study Example S3
Desired accuracy with Desired accuracy with 5%5%Confidence level Confidence level = 95%= 95%Sample standard deviation Sample standard deviation = 1.0= 1.0Sample mean Sample mean = 3.00= 3.00
n = n = 22
zszshxhx
n n = = 170.74 ≈ 171= = 170.74 ≈ 17122
1.96 x 1.01.96 x 1.0.05 x 3.05 x 3
h h = .05= .05 x x = 3.00= 3.00 s s = 1.0= 1.0
zz = 1.96 ( = 1.96 (from from Table S10.1Table S10.1 or Appendix I or Appendix I))
© 2006 Prentice Hall, Inc. S10 – 26
New ToolsNew Tools
With this PDA, you With this PDA, you can study elements, can study elements, time, performance time, performance rate, and statistical rate, and statistical confidence intervals confidence intervals can be created, can be created, edited, managed, and edited, managed, and downloaded to a downloaded to a spreadsheetspreadsheet
© 2006 Prentice Hall, Inc. S10 – 27
Predetermined Time Predetermined Time StandardsStandards
Divide manual work into small basic Divide manual work into small basic elements that have established timeselements that have established times
Can be done in a laboratory away from Can be done in a laboratory away from the actual production operationthe actual production operation
Can be set before the work is actually Can be set before the work is actually performedperformed
No performance ratings are necessaryNo performance ratings are necessary
© 2006 Prentice Hall, Inc. S10 – 28
MTM TableMTM Table
Figure S10.2Figure S10.2
© 2006 Prentice Hall, Inc. S10 – 29
MTM ExampleMTM Example
Weight - less than 2 poundsWeight - less than 2 poundsConditions of GET - easyConditions of GET - easyPlace accuracy - approximatePlace accuracy - approximateDistance range - 8 to 20 inchesDistance range - 8 to 20 inches
Element DescriptionElement Description ElementElement TimeTime
Get tube from rackGet tube from rack AA2AA2 3535
Get stopper, place on counterGet stopper, place on counter AA2AA2 3535
Get centrifuge tube, place at sample tableGet centrifuge tube, place at sample table AD2AD2 4545
Pour (3 seconds)Pour (3 seconds) PTPT 8383
Place tubes in rackPlace tubes in rack PC2PC2 4040
Total TMUTotal TMU 238238
.0006 x 238 =.0006 x 238 = Total standard mins Total standard mins = .14= .14
Table S10.2Table S10.2
© 2006 Prentice Hall, Inc. S10 – 30
Work SamplingWork Sampling
Estimates percent of time a worker Estimates percent of time a worker spends on various tasksspends on various tasks Less expensive than time studyLess expensive than time study
Observers need little trainingObservers need little training
Studies can be delayed or interrupted Studies can be delayed or interrupted with little impact on resultswith little impact on results
Worker has little chance to affect Worker has little chance to affect resultsresults
Less intrusiveLess intrusive
© 2006 Prentice Hall, Inc. S10 – 31
Work SamplingWork Sampling
Estimates percent of time a worker Estimates percent of time a worker spends on various tasksspends on various tasks Does not divide work elements as Does not divide work elements as
completely as time studycompletely as time study
Can yield biased results if observer Can yield biased results if observer does not follow random patterndoes not follow random pattern
Less accurate than time study, Less accurate than time study, especially when job element times especially when job element times are shortare short
© 2006 Prentice Hall, Inc. S10 – 32
Work SamplingWork Sampling
1.1. Take a preliminary sample to obtain Take a preliminary sample to obtain estimates of parameter valuesestimates of parameter values
2.2. Compute the sample size requiredCompute the sample size required
3.3. Prepare a schedule for random Prepare a schedule for random observations at appropriate timesobservations at appropriate times
4.4. Observe and record worker activitiesObserve and record worker activities
5.5. Determine how workers spend their Determine how workers spend their timetime
© 2006 Prentice Hall, Inc. S10 – 33
Work SamplingWork Sampling
Determining the sample sizeDetermining the sample size
n =n =zz22 p p(1 -(1 - p p))
hh22
wherewhere nn == required sample sizerequired sample size
zz == standard normal standard normal deviate for desired confidence deviate for desired confidence levellevel
pp == estimated value of estimated value of sample proportionsample proportion
hh == acceptable error acceptable error level in percentlevel in percent
© 2006 Prentice Hall, Inc. S10 – 34
Work SamplingWork Sampling
Estimate employees idle 25% of the timeEstimate employees idle 25% of the timeSample should be accurate within 3%Sample should be accurate within 3%Wants to have 95.45% confidence in the resultsWants to have 95.45% confidence in the results
n =n =zz22 p p(1 -(1 - p p))
hh22
wherewhere nn == required sample sizerequired sample sizezz == 22 for a for a 95.45%95.45% confidence levelconfidence levelpp == estimate of idle estimate of idle proportion proportion = 25% = .25= 25% = .25hh == acceptable error of acceptable error of 3% 3% = .03= .03n n = = 833= = 833 observations observations
(2)(2)22 (.25)(.75) (.25)(.75)
(.03)(.03)22
© 2006 Prentice Hall, Inc. S10 – 35
Work SamplingWork SamplingNo. of No. of
ObservationsObservations ActivityActivity
485485 On the phone or meeting with a welfare clientOn the phone or meeting with a welfare client
126126 IdleIdle
6262 Personal timePersonal time
2323 Discussions with supervisorDiscussions with supervisor
137137 Filing, meeting, and computer data entryFiling, meeting, and computer data entry
833833
All but idle and personal time are work related. All but idle and personal time are work related. Percentage idle time Percentage idle time = (126 + 62)/833 = 22.6%.= (126 + 62)/833 = 22.6%. Since this is less than the target value of Since this is less than the target value of 25%,25%, the workload needs to be adjusted.the workload needs to be adjusted.
© 2006 Prentice Hall, Inc. S10 – 36
Work SamplingWork Sampling
1.1. Take a preliminary sample to obtain Take a preliminary sample to obtain estimates of parameter valuesestimates of parameter values
2.2. Compute the sample size requiredCompute the sample size required
3.3. Prepare a schedule for random Prepare a schedule for random observations at appropriate timesobservations at appropriate times
4.4. Observe and record worker activitiesObserve and record worker activities
5.5. Determine how workers spend their Determine how workers spend their timetime
© 2006 Prentice Hall, Inc. S10 – 37
Work Sampling Time Work Sampling Time StudiesStudies
SalespeopleSalespeople
Figure S10.3Figure S10.3
Telephone Telephone salessales12%12%
Telephone Telephone within firmwithin firm
13%13%
Lunch and Lunch and personalpersonal
10%10%
Meetings Meetings and otherand other
8%8%
Paperwork17%
Travel20%
Sales in person
20%
© 2006 Prentice Hall, Inc. S10 – 38
Work Sampling Time Work Sampling Time StudiesStudies
Figure S10.3Figure S10.3
Productive work67%
Startup/pep talkStartup/pep talk3%3%
Breaks and lunchBreaks and lunch10%10%
Dead time Dead time between tasksbetween tasks
13%13%
CleanupCleanup3%3%
Unscheduled tasks Unscheduled tasks and downtimeand downtime
4%4%
Assembly-Line Assembly-Line EmployeesEmployees