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© 2008 Prentice Hall, Inc. S10 – 1

Operations ManagementSupplement 10 – Supplement 10 – Work MeasurementWork Measurement

PowerPoint presentation to accompany PowerPoint presentation to accompany Heizer/Render Heizer/Render Principles of Operations Management, 7ePrinciples of Operations Management, 7eOperations Management, 9e Operations Management, 9e


OutlineOutline Labor Standards and Work Labor Standards and Work

MeasurementMeasurement Historical ExperienceHistorical Experience Time StudiesTime Studies Predetermined Time Predetermined Time

StandardsStandards Work SamplingWork Sampling


Learning ObjectivesLearning ObjectivesWhen you complete this supplement When you complete this supplement you should be able to:you should be able to: Identify four ways of establishing labor Identify four ways of establishing labor

standardsstandards Compute the normal and standard Compute the normal and standard

times in a time studytimes in a time study Find the proper sample size for a time Find the proper sample size for a time

studystudy


Learning ObjectivesLearning ObjectivesWhen you complete this supplement When you complete this supplement you should be able to:you should be able to: Explain how predetermined time Explain how predetermined time

standards and TMUs are used in work standards and TMUs are used in work measurementmeasurement

Apply the five steps of work samplingApply the five steps of work sampling


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


Meaningful Standards Help Meaningful Standards Help DetermineDetermine

1.1. Labor content of items producedLabor content of items produced2.2. Staffing needsStaffing needs3.3. Cost and time estimatesCost and time estimates4.4. Crew size and work balanceCrew size and work balance5.5. Expected productionExpected production6.6. Basis of wage incentive plansBasis of wage incentive plans7.7. Efficiency of employeesEfficiency of employees


Labor StandardsLabor Standards

May be set in four ways:May be set in four ways:

1.1. Historical experienceHistorical experience2.2. Time studiesTime studies3.3. Predetermined time standardsPredetermined time standards4.4. Work samplingWork sampling


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


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



1.1. Define the task to be studiedDefine the task to be studied2.2. Divide the task into precise Divide the task into precise

elementselements3.3. Decide how many times to measure Decide how many times to measure

the taskthe task4.4. Time and record element times and Time and record element times and

rating of performancerating of performance



5.5. Compute average observed timeCompute average observed time

Average Average observed observed

timetime

Sum of the times recorded Sum of the times recorded to perform each elementto perform each elementNumber of observationsNumber of observations==

6.6. Determine performance rating Determine performance rating and normal timeand normal time

Normal time = xNormal time = xAverage Average

observed observed timetime

Performance Performance rating factorrating factor



7.7. Add the normal times for each Add 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 time1 -1 - Allowance factor Allowance factor


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


Rest AllowancesRest Allowances1.1. Constant allowanceConstant allowance

(A)(A) Personal allowance ……………...Personal allowance ……………...

55(B)(B) Basic fatigue allowance …………Basic fatigue allowance …………

442.2. 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


Rest AllowancesRest Allowances(C)(C) Use of force or muscular energy in Use of force or muscular energy in

lifting, pulling, pushinglifting, pulling, pushingWeight lifted (pounds)Weight lifted (pounds)20 ……………………………………20 ……………………………………

3340…………………………………….40…………………………………….

9960…………………………………….60…………………………………….

1717(D)(D) Bad light:Bad light:

(i)(i) Well below recommended….Well below recommended….

22(ii)(ii) Quite inadequate…………….Quite inadequate…………….

55



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



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



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


Time Study Example S2Time Study Example S2Allowance 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 times for each elementCompute average 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


Time Study Example S2Time Study Example S23.3. 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


Time Study Example S2Time Study Example S25.5. Compute the standard time for the jobCompute the standard time for the job

Standard time =Standard time = Total normal timeTotal normal time1 -1 - Allowance factor Allowance factor

= = 18.07= = 18.07 minutes minutes15.3615.361 - .151 - .15


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



Required sample size = n = Required sample size = n = 22zszs

hxhx

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 decimalzz == number of standard number of standard deviations required for the desired level deviations required for the desired level of confidenceof confidencess == standard deviation of the standard deviation of the initial sampleinitial samplexx == mean of the initial samplemean of the initial samplenn == required sample sizerequired sample size



Required sample size = n = Required sample size = n = 22zszs

hxhx

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 decimalzz == number of standard number of standard deviations required for the desired level deviations required for the desired level of confidenceof confidencess == standard deviation of the standard deviation of the initial sampleinitial samplexx == mean of the initial samplemean of the initial samplenn == required sample sizerequired sample size

Desired Confidence

(%)

z Value (standard deviation required for

desired level of confidence)90.0 1.6595.0 1.9695.45 2.0099.0 2.5899.73 3.00

Common z Values

Table S10.1


Time Study Example S3Time Study Example S3Desired 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 = 22zszs

hxhx

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= 1.0zz = 1.96 ( = 1.96 (from from Table S10.1Table S10.1 or Appendix I or Appendix I))


Time Study Example S3Time Study Example S3

n = n = 22zszs

ee

If desired accuracy h is expressed as an absolute If desired accuracy h is expressed as an absolute amount, substitute e for hx, where e is the amount, substitute e for hx, where e is the absolute amount of acceptable errorabsolute amount of acceptable error

VariationsVariations

When the standard deviation s is not provided, When the standard deviation s is not provided, it must be computedit must be computed

s = = s = = ∑∑(x(xii - x) - x)22 ∑∑(Each sample observation - x)(Each sample observation - x)22

n n - 1- 1 Number in sampleNumber in sample - 1 - 1


New ToolsNew Tools With PDA software, you can study With PDA software, you can study

elements, time, performance rate, and elements, time, performance rate, and statistical confidence intervals can be statistical confidence intervals can be created, created, edited, edited, managed, managed, and loggedand logged

Reduces or Reduces or eliminates eliminates the need the need for data entryfor data entry


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 Can be set before the work is actually the work is actually performedperformed

No performance No performance ratings are necessaryratings are necessary


MTM TableMTM Table



MTM ExampleMTM ExampleWeight - 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 TimeTimeGet tube from rackGet tube from rack AA2AA2 3535Get stopper, place on counterGet stopper, place on counter AA2AA2 3535Get centrifuge tube, place at sample tableGet centrifuge tube, place at sample table AD2AD2 4545Pour (3 seconds)Pour (3 seconds) PTPT 8383Place tubes in rack (simo)Place tubes in rack (simo) PC2PC2 4040

Total TMUTotal TMU 238238.0006 x 238 =.0006 x 238 = Total standard minutes Total standard minutes = .14= .14

Table S10.2Table S10.2


Work SamplingWork Sampling Estimates percent of time a worker Estimates percent of time a worker

spends on various tasksspends on various tasks Requires random observations to Requires random observations to

record worker activityrecord worker activity Determines how employees allocate Determines how employees allocate

their timetheir time Can be used to set staffing levels, Can be used to set staffing levels,

reassign duties, estimate costs, and reassign duties, estimate costs, and set delay allowancesset delay allowances


Work SamplingWork Sampling Advantages of work samplingAdvantages of work sampling

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 Worker has little

chance to affect chance to affect resultsresults

Less intrusiveLess intrusive


Disadvantages of work samplingDisadvantages of work sampling 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, especially when Less accurate, especially when

job element times are shortjob element times are short

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 required3.3. Prepare a schedule for random Prepare a schedule for random

observations at appropriate timesobservations at appropriate times4.4. Observe and record worker activitiesObserve and record worker activities5.5. Determine how workers spend their Determine how workers spend their

timetime



Determining the sample sizeDetermining the sample size

n =n = zz22 p p(1 -(1 - p p))hh22

wherewhere nn == required sample sizerequired sample sizezz == standard normal standard normal deviate for desired confidence deviate for desired confidence levellevelpp == estimated value of estimated value of sample proportionsample proportionhh == acceptable error acceptable error level in percentlevel in percent


Work Sampling ExampleWork Sampling ExampleWants employees idle 25% of the timeWants 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


Work Sampling ExampleWork Sampling ExampleNo. of No. of

ObservationsObservations ActivityActivity485485 On the phone or meeting with a welfare clientOn the phone or meeting with a welfare client126126 IdleIdle6262 Personal timePersonal time2323 Discussions with supervisorDiscussions with supervisor137137 Filing, meeting, and computer data entryFiling, meeting, and computer data entry833833

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.


Work Sampling Time Work Sampling Time StudiesStudies

SalespeopleSalespeople


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%


Work Sampling Time Work Sampling Time StudiesStudies


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

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