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© 2008 Prentice Hall, Inc.S10 – 1 Operations Management Supplement 10 – Work Measurement PowerPoint presentation to accompany Heizer/Render Principles of Operations Management, 7e Operations Management, 9e

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© 2008 Prentice Hall, Inc.S10 – 2 Outline Labor Standards and Work Measurement Labor Standards and Work Measurement Historical Experience Historical Experience Time Studies Time Studies Predetermined Time Standards Predetermined Time Standards Work Sampling Work Sampling

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© 2008 Prentice Hall, Inc.S10 – 3 Learning Objectives When you complete this supplement you should be able to: Identify four ways of establishing labor standards Identify four ways of establishing labor standards Compute the normal and standard times in a time study Compute the normal and standard times in a time study Find the proper sample size for a time study Find the proper sample size for a time study

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© 2008 Prentice Hall, Inc.S10 – 4 Learning Objectives When you complete this supplement you should be able to: Explain how predetermined time standards and TMUs are used in work measurement Explain how predetermined time standards and TMUs are used in work measurement Apply the five steps of work sampling Apply the five steps of work sampling

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© 2008 Prentice Hall, Inc.S10 – 5 Labor Standards and Work Measurement Started early in the 20th century Started early in the 20th century Important to both manufacturing and service organizations Important to both manufacturing and service organizations Necessary for determining staffing requirements Necessary for determining staffing requirements Important to labor incentive systems Important to labor incentive systems

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© 2008 Prentice Hall, Inc.S10 – 6 Meaningful Standards Help Determine 1.Labor content of items produced 2.Staffing needs 3.Cost and time estimates 4.Crew size and work balance 5.Expected production 6.Basis of wage incentive plans 7.Efficiency of employees

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© 2008 Prentice Hall, Inc.S10 – 7 Labor Standards May be set in four ways: 1.Historical experience 2.Time studies 3.Predetermined time standards 4.Work sampling

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© 2008 Prentice Hall, Inc.S10 – 8 Historical Experience How the task was performed last time How the task was performed last time Easy and inexpensive Easy and inexpensive Data available from production records or time cards Data available from production records or time cards Data is not objective and may be inaccurate Data is not objective and may be inaccurate Not recommended Not recommended

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© 2008 Prentice Hall, Inc.S10 – 9 Time Studies Involves timing a sample of a workers performance and using it to set a standard Involves timing a sample of a workers performance and using it to set a standard Requires trained and experienced observers Requires trained and experienced observers Cannot be set before the work is performed Cannot be set before the work is performed

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© 2008 Prentice Hall, Inc.S10 – 10 Time Studies 1.Define the task to be studied 2.Divide the task into precise elements 3.Decide how many times to measure the task 4.Time and record element times and rating of performance

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© 2008 Prentice Hall, Inc.S10 – 11 Time Studies 5.Compute average observed time Average observed time Sum of the times recorded to perform each element Number of observations = 6.Determine performance rating and normal time Normal time = x Average observed time Performance rating factor

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© 2008 Prentice Hall, Inc.S10 – 12 Time Studies 7.Add the normal times for each element to develop the total normal time for the task 8.Compute the standard time Standard time = Total normal time 1 - Allowance factor

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© 2008 Prentice Hall, Inc.S10 – 13 Rest Allowances Personal time allowance Personal time allowance 4% - 7% of total time for use of restroom, water fountain, etc. 4% - 7% of total time for use of restroom, water fountain, etc. Delay allowance Delay allowance Based upon actual delays that occur Based upon actual delays that occur Fatigue allowance Fatigue allowance Based on our knowledge of human energy expenditure Based on our knowledge of human energy expenditure

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© 2008 Prentice Hall, Inc.S10 – 14 Rest Allowances 1.Constant allowance (A)Personal allowance ……………...5 (B)Basic fatigue allowance …………4 2.Variable allowances: (A)Standing allowance ………………2 (B)Abnormal position (i)Awkward (bending) …………2 (ii)Very awkward (lying, stretching) ……………………7 Figure S10.1

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© 2008 Prentice Hall, Inc.S10 – 15 Rest Allowances (C)Use of force or muscular energy in lifting, pulling, pushing Weight lifted (pounds) 20 ……………………………………3 40…………………………………….9 60…………………………………….17 (D)Bad light: (i)Well below recommended….2 (ii) Quite inadequate…………….5 Figure S10.1

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© 2008 Prentice Hall, Inc.S10 – 16 Rest Allowances (E)Atmospheric conditions (heat and humidity) ……………0-10 (F)Close attention: (i) Fine or exacting………………..2 (ii) Very fine or very exacting……5 (G)Noise level: (i) Intermittentloud……………..2 (ii) Intermittentvery loud or high-pitched………………...5 Figure S10.1

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© 2008 Prentice Hall, Inc.S10 – 17 Rest Allowances (H)Mental strain: (i) Complex or wide span of attention.……………………..4 (ii) Very complex…………………..8 (I)Tediousness: (i) Tedious…………..………………2 (ii) Very tedious.……………………5 Figure S10.1

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© 2008 Prentice Hall, Inc.S10 – 18 Time Study Example S1 Average observed time = 4.0 minutes Worker rating = 85% Allowance factor = 13% Normal time = (Average observed time) x (Rating factor) = (4.0)(.85) = 3.4 minutes Standard time = = = Normal time 1 - Allowance factor 3.4 1 -.13 3.4.87 = 3.9 minutes

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© 2008 Prentice Hall, Inc.S10 – 19 Time Study Example S2 Allowance factor = 15% Performance Job Element12345Rating (A)Compose and type letter8109 21*11120% (B)Type envelope address232 1 3105% (C)Stuff, stamp, seal, and215*2 1110% sort envelopes Cycle Observed (in minutes) 1.Delete unusual or nonrecurring observations (marked with *) 2.Compute average times for each element Average time for A = (8 + 10 + 9 + 11)/4 = 9.5 minutes Average time for B = (2 + 3 + 2 + 1 + 3)/5 = 2.2 minutes Average time for C = (2 + 1 + 2 + 1)/4 = 1.5 minutes

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© 2008 Prentice Hall, Inc.S10 – 20 Time Study Example S2 3.Compute the normal time for each element Normal time for A = (9.5)(1.2) = 11.4 minutes Normal time for B = (2.2)(1.05) = 2.31 minutes Normal time for C = (1.5)(1.10) = 1.65 minutes Normal time = (Average observed time) x (Rating) 4.Add the normal times to find the total normal time Total normal time = 11.40 + 2.31 + 1.65 = 15.36 minutes

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© 2008 Prentice Hall, Inc.S10 – 21 Time Study Example S2 5.Compute the standard time for the job Standard time = Total normal time 1 - Allowance factor = = 18.07 minutes 15.36 1 -.15

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© 2008 Prentice Hall, Inc.S10 – 22 Determine Sample Size How accurate we want to be How accurate we want to be The desired level of confidence The desired level of confidence How much variation exists within the job elements How much variation exists within the job elements

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© 2008 Prentice Hall, Inc.S10 – 23 Determine Sample Size Required sample size = n = 2zshx whereh=accuracy level desired in percent of the job element expressed as a decimal z=number of standard deviations required for the desired level of confidence s=standard deviation of the initial sample x=mean of the initial sample n=required sample size

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© 2008 Prentice Hall, Inc.S10 – 24 Determine Sample Size Required sample size = n = 2zshx whereh=accuracy level desired in percent of the job element expressed as a decimal z=number of standard deviations required for the desired level of confidence s=standard deviation of the initial sample x=mean of the initial sample n=required sample size Desired Confidence (%) z Value (standard deviation required for desired level of confidence) 90.01.65 95.01.96 95.452.00 99.02.58 99.733.00 Common z Values Table S10.1

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© 2008 Prentice Hall, Inc.S10 – 25 Time Study Example S3 Desired accuracy with 5% Confidence level = 95% Sample standard deviation = 1.0 Sample mean = 3.00 n = 2zshx n = = 170.74 171 2 1.96 x 1.0.05 x 3 h =.05x = 3.00s = 1.0 z = 1.96 (from Table S10.1 or Appendix I)

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© 2008 Prentice Hall, Inc.S10 – 26 Time Study Example S3 n = 2zse If desired accuracy h is expressed as an absolute amount, substitute e for hx, where e is the absolute amount of acceptable error Variations When the standard deviation s is not provided, it must be computed s = = (x i - x) 2 (Each sample observation - x) 2 (x i - x) 2 (Each sample observation - x) 2 n - 1Number in sample - 1

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© 2008 Prentice Hall, Inc.S10 – 27 New Tools With PDA software, you can study elements, time, performance rate, and statistical confidence intervals can be created, edited, managed, and logged With PDA software, you can study elements, time, performance rate, and statistical confidence intervals can be created, edited, managed, and logged Reduces or eliminates the need for data entry Reduces or eliminates the need for data entry

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© 2008 Prentice Hall, Inc.S10 – 28 Predetermined Time Standards Divide manual work into small basic elements that have established times Divide manual work into small basic elements that have established times Can be done in a laboratory away from the actual production operation Can be done in a laboratory away from the actual production operation Can be set before the work is actually performed Can be set before the work is actually performed No performance ratings are necessary No performance ratings are necessary

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© 2008 Prentice Hall, Inc.S10 – 29 MTM Table Figure S10.2

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© 2008 Prentice Hall, Inc.S10 – 30 MTM Example Weight - less than 2 pounds Conditions of GET - easy Place accuracy - approximate Distance range - 8 to 20 inches Element Description ElementTime Get tube from rack AA235 Get stopper, place on counter AA235 Get centrifuge tube, place at sample table AD245 Pour (3 seconds) PT83 Place tubes in rack (simo) PC240 Total TMU 238.0006 x 238 = Total standard minutes =.14 Table S10.2

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© 2008 Prentice Hall, Inc.S10 – 31 Work Sampling Estimates percent of time a worker spends on various tasks Estimates percent of time a worker spends on various tasks Requires random observations to record worker activity Requires random observations to record worker activity Determines how employees allocate their time Determines how employees allocate their time Can be used to set staffing levels, reassign duties, estimate costs, and set delay allowances Can be used to set staffing levels, reassign duties, estimate costs, and set delay allowances

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© 2008 Prentice Hall, Inc.S10 – 32 Work Sampling Advantages of work sampling Advantages of work sampling Less expensive than time study Less expensive than time study Observers need little training Observers need little training Studies can be delayed or interrupted with little impact on results Studies can be delayed or interrupted with little impact on results Worker has little chance to affect results Worker has little chance to affect results Less intrusive Less intrusive

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© 2008 Prentice Hall, Inc.S10 – 33 Disadvantages of work sampling Disadvantages of work sampling Does not divide work elements as completely as time study Does not divide work elements as completely as time study Can yield biased results if observer does not follow random pattern Can yield biased results if observer does not follow random pattern Less accurate, especially when job element times are short Less accurate, especially when job element times are short Work Sampling

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© 2008 Prentice Hall, Inc.S10 – 34 Work Sampling 1.Take a preliminary sample to obtain estimates of parameter values 2.Compute the sample size required 3.Prepare a schedule for random observations at appropriate times 4.Observe and record worker activities 5.Determine how workers spend their time

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© 2008 Prentice Hall, Inc.S10 – 35 Work Sampling Determining the sample size n = z 2 p(1 - p) h 2 wheren=required sample size z=standard normal deviate for desired confidence level p=estimated value of sample proportion h=acceptable error level in percent

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© 2008 Prentice Hall, Inc.S10 – 36 Work Sampling Example Wants employees idle 25% of the time Sample should be accurate within 3% Wants to have 95.45% confidence in the results n = z 2 p(1 - p) h 2 wheren=required sample size z=2 for a 95.45% confidence level p=estimate of idle proportion = 25% =.25 h=acceptable error of 3% =.03 n = = 833 observations (2) 2 (.25)(.75) (.03) 2

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© 2008 Prentice Hall, Inc.S10 – 37 Work Sampling Example No. of Observations Activity 485 On the phone or meeting with a welfare client 126Idle 62 Personal time 23 Discussions with supervisor 137 Filing, meeting, and computer data entry 833 All but idle and personal time are work related. Percentage idle time = (126 + 62)/833 = 22.6%. Since this is less than the target value of 25%, the workload needs to be adjusted.

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© 2008 Prentice Hall, Inc.S10 – 38 Work Sampling Time Studies Salespeople Figure S10.3 Telephone sales 12% Telephone within firm 13% Lunch and personal 10% Meetings and other 8% Paperwork 17% Travel 20% Sales in person 20%

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© 2008 Prentice Hall, Inc.S10 – 39 Work Sampling Time Studies Figure S10.3 Productive work 67% Startup/pep talk 3% Breaks and lunch 10% Dead time between tasks 13% Cleanup3% Unscheduled tasks and downtime 4% Assembly-Line Employees

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