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Chapter 8 supplement, work measurement. In this supplement, you will learn about time studies and work sampling. Work measurement is determining how long it takes to do a job. Managing human resources requires managers to know how much work employees can do during a specific period.
OPERATIONS MANAGEMENT: Creating Value Along the Supply Chain, Canadian Edition Robert S Russell, Bernard W Taylor III, Ignacio Castillo, Navneet Vidyarthi CHAPTER SUPPLEMENT Work Measurement Supplement 8-1 Lecture Outline Time Studies Work Sampling Supplement 8-2 Work Measurement Determining how long it takes to a job Growing importance in service sector Services tend to be labor-intensive Service jobs are often repetitive Time studies Standard time • time for average worker to perform a job once Incentive piece-rate wage system based on time study Supplement 8-3 Stopwatch Time Study - Steps Establish standard job method Break down job into elements Study job Rate worker’s performance (RF) Compute average time (t) Supplement 8-4 Stopwatch Time Study - Steps Compute normal time Normal Time = (Elemental average) x (rating factor) Nt = (t )(RF) Normal Cycle Time = NT = Nt Compute standard time Standard Time = (normal cycle time) x (1 + allowance factor) ST = (NT)(1 + AF) Supplement 8-5 Performing a Time Study Time Study Observation Sheet Identification of operation Date Sandwich Assembly Operator Smith Approval Jones Observer Russell Cycles Grasp and lay out bread slices Spread mayonnaise on both slices Place ham, cheese, and lettuce on bread Place top on sandwich, Slice, and stack t Summary 10 04 05 05 04 06 05 06 06 07 05 R 04 38 72 1.05 1.40 1.76 2.13 2.50 2.89 3.29 t 07 06 R 11 44 79 1.13 1.47 1.83 2.21 2.60 2.98 3.37 t 12 11 07 08 07 07 14 12 13 13 08 13 10 12 09 14 08 93 1.25 1.60 1.96 2.34 2.72 3.12 3.51 t 10 12 08 R 33 67 1.01 1.34 1.71 2.07 2.44 2.82 3.24 3.61 11 11 10 10 12 t t RF Nt 53 053 1.05 056 77 077 1.00 077 14 1.28 1.28 1.10 141 R 23 55 09 5/17 10 1.03 1.03 1.10 113 Supplement 8-6 Performing a Time Study Average element time = t = 0.53 Σt = = 0.053 10 10 Normal time = (Elemental average)(rating factor) Nt = ( t )(RF) = (0.053)(1.05) = 0.056 Normal Cycle Time = NT = Nt = 0.387 ST = (NT) (1 + AF) = (0.387)(1+0.15) = 0.445 Supplement 8-7 Performing a Time Study How many sandwiches can be made in hours? 120 0.445 min/sandwich = 269.7 or 270 sandwiches Supplement 8-8 Incentive Piece-Rate System Average worker makes 135 sandwiches per hour 60 0.445 min/sandwich = 134.8 or 135 sandwiches Average hourly wage rate is 135 x 0.04 = $5.40 Supplement 8-9 Example Worker Wages Observed worker average cycle time = 0.361, no RF 0.361 x (1+0.15) = 0.414 60 0.415 min/sandwich = 144.6 or 145 sandwiches Average hourly wage rate is 145 x 0.04 = $5.80 Supplement 8-10 Time Study With Excel Supplement 8-11 Number of Cycles Computing number of job cycles to observe: n= zs eT where z= number of standard deviations from the mean in a normal distribution reflecting a level of statistical confidence sΣ(xi = - x)2 n-1 T= study e= = sample standard deviation from sample time study average job cycle time from the sample time degree of error from true mean of distribution Supplement 8-12 Number of Cycles • • • Average cycle time = 0.361 Computed standard deviation = 0.03 Company wants to be 95% confident that computed time is within 5% of true average time zs neT = = (1.96)(0.03) (0.05)(0.361) = 10.61 or 11 Supplement 8-13 Number of Cycles With Excel Sample size Supplement 8-14 Developing Time Standards Without a Time Study Elemental standard Advantages time files • worker cooperation • predetermined job unnecessary element times • workplace uninterrupted Predetermined • performance ratings motion times unnecessary • predetermined times • consistent for basic micro-motions Disadvantages Time measurement units • ignores job context • TMUs = 0.0006 minute • may not reflect skills and • 100,000 TMU = hour abilities of local workers Supplement 8-15 MTM Table for MOVE TIME (TMU) WEIGHT ALLOWANCE DISTANCE Hand in Weight Static MOVED motion (lb) Dynamic constant (INCHES) A B C B up to: factor TMU 3/4 or less 2.0 2.0 2.0 2.5 2.9 3.4 2.3 2.5 1.00 3.6 4.6 5.2 2.9 4.9 5.7 6.7 3.6 7.5 1.06 2.2 6.1 6.9 8.0 4.3 … 20 19.2 18.2 22.1 15.6 37.5 1.39 12.5 A Move object to other hand or against stop MTM Association for Standards and Research B Move object to approximate or indefinite Source: location C Move object to exact location Supplement 8-16 Work Sampling Determines the proportion of time a worker spends on activities Primary uses of work sampling are to determine ratio delay • percentage of time a worker or machine is delayed or idle analyze jobs that have non-repetitive tasks Cheaper, easier approach to work measurement Supplement 8-17 Steps of Work Sampling Define job activities Determine number of observations in work sample z n= e p(1 - p) where n= sample size (number of sample observations) z= number of standard deviations from mean for desired level of confidence e= degree of allowable error in sample estimate p= proportion of time spent on a work activity estimated prior to calculating work sample Supplement 8-18 Steps of Work Sampling Determine length of sampling period Conduct work sampling study; record observations Periodically re-compute number of observations Supplement 8-19 Work Sampling What percent of time is spent looking up information? Current estimate is p = 30% Estimate within +/- 2%, with 95% confidence n= z e p(1 - p) = 1.96 0.02 (0.3)(0.7) = 2016.84 or 2017 After 280 observations, p = 38% n= z e p(1 - p) = 1.96 (0.38)(0.62) = 2263 0.02 Supplement 8-20 Work Sampling With OM Tools Supplement 8-21 COPYRIGHT COPYRIGHT Copyright © 2014 John Wiley & Sons Canada, Ltd All rights reserved Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd The purchaser may make back-up copies for his or her own use only and not for distribution or resale The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein ... for distribution or resale The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained... within + /- 2%, with 95% confidence n= z e p(1 - p) = 1.96 0.02 (0.3)(0.7) = 2016.84 or 2017 After 280 observations, p = 38% n= z e p(1 - p) = 1.96 (0.38)(0.62) = 2263 0.02 Supplement 8-2 0 Work... Agency) is unlawful Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd The purchaser may make back-up copies for his or her own use