measuring output rates

© 2007 Pearson Education

MeasuringOutput Rates

Supplement HSupplement H


Work Standards

A work standard is the time required for a trained worker to perform a task following a prescribed method with normal effort and skill.

Used in the following ways: Establishing prices and costs. Motivating workers. Comparing alternative process designs. Scheduling. Capacity planning. Performance appraisal.


Methods of Work Measurement

The time study method. The elemental standard data approach.The predetermined data approach.The work sampling method.


The Time Study Method

Time study is the method used most often.

Step 1: Selecting the work elements.

Step 2: Timing the elements.

Step 3: Determining sample size.

Step 4: Setting the standard.


Time Study MethodTime Study MethodExample H.1Example H.1

Packaging Coffee Cups


Step 1: Selecting Work ElementsStep 1: Selecting Work Elements

Work ElementWork Element

1.1. Get two cartonsGet two cartons2.2. Put liner in cartonPut liner in carton3.3. Place cups in cartonPlace cups in carton4.4. Seal carton and set asideSeal carton and set aside



Step 2: Timing the ElementsStep 2: Timing the Elements (10 observations)(10 observations)

StandardStandard SelectSelectDeviation, Deviation, Time, Time, tt

Work ElementWork Element (minutes)(minutes) (minutes)(minutes)

1.1. Get two cartonsGet two cartons 0.03050.0305 0.500.502.2. Put liner in cartonPut liner in carton 0.01710.0171 0.110.113.3. Place cups in cartonPlace cups in carton 0.02260.0226 0.710.714.4. Seal carton and set asideSeal carton and set aside 0.02410.0241 1.101.10

Work element 1 was observed only 5 times because it occurs once every two work cycles.



Step 3: Determining the Sample SizeStep 3: Determining the Sample Size

nn = = [( )( )][( )( )]zz p tp t

22

StandardStandard SelectSelect RequiredRequiredDeviation, Deviation, Time, Time, tt SampleSample

Work ElementWork Element (minutes)(minutes) (minutes)(minutes) SizeSize








nn = = [( )( )][( )( )]zz p tp t

22

DesiredConfidence (%) z

90 1.6595 1.9696 2.0597 2.1798 2.3399 2.58

p = 0.04 z = 1.96







1.961.96 0.040.04 t tnn = = [( )( )][( )( )]

22







nn = = [( )( )][( )( )]1.96 0.03051.96 0.03050.04 0.5000.04 0.500

22






1.1. Get two cartonsGet two cartons 0.03050.0305 0.500.50 992.2. Put liner in cartonPut liner in carton 0.01710.0171 0.110.113.3. Place cups in cartonPlace cups in carton 0.02260.0226 0.710.714.4. Seal carton and set asideSeal carton and set aside 0.02410.0241 1.101.10

1.961.96 0.040.04 t tnn = = [( )( )][( )( )]

22






1.1. Get two cartonsGet two cartons 0.03050.0305 0.500.50 992.2. Put liner in cartonPut liner in carton 0.01710.0171 0.110.11 58583.3. Place cups in cartonPlace cups in carton 0.02260.0226 0.710.714.4. Seal carton and set asideSeal carton and set aside 0.02410.0241 1.101.10

1.961.96 0.040.04 t tnn = = [( )( )][( )( )]

22






1.1. Get two cartonsGet two cartons 0.03050.0305 0.500.50 992.2. Put liner in cartonPut liner in carton 0.01710.0171 0.110.11 58583.3. Place cups in cartonPlace cups in carton 0.02260.0226 0.710.71 334.4. Seal carton and set asideSeal carton and set aside 0.02410.0241 1.101.10

1.961.96 0.040.04 t tnn = = [( )( )][( )( )]

22



Step 3: Determining the Sample Step 3: Determining the Sample SizeSize



1.1. Get two cartonsGet two cartons 0.03050.0305 0.500.50 992.2. Put liner in cartonPut liner in carton 0.01710.0171 0.110.11 58583.3. Place cups in cartonPlace cups in carton 0.02260.0226 0.710.71 334.4. Seal carton and set asideSeal carton and set aside 0.02410.0241 1.101.10 22

1.961.96 0.040.04 t tnn = = [( )( )][( )( )]

22






1.1. Get two cartonsGet two cartons 0.03050.0305 0.500.50 992.2. Put liner in cartonPut liner in carton 0.01710.0171 0.110.11 58583.3. Place cups in cartonPlace cups in carton 0.02260.0226 0.710.71 334.4. Seal carton and set asideSeal carton and set aside 0.02410.0241 1.101.10 22

Use largest n, 58.



Step 4: Setting the StandardStep 4: Setting the Standard

Work ElementWork Element tt FF RFRF NTNT

1.1. Get two cartonsGet two cartons2.2. Put liner in cartonPut liner in carton3.3. Place cups in cartonPlace cups in carton4.4. Seal carton and set asideSeal carton and set aside



Step 4: Setting the StandardStep 4: Setting the Standard (after 48 additional observations)(after 48 additional observations)

Performance rating factor (RF) describes Performance rating factor (RF) describes how muchhow much above or below the average. above or below the average.


1.1. Get two cartonsGet two cartons 0.530.53 0.500.50 1.051.052.2. Put liner in cartonPut liner in carton 0.100.10 1.001.00 0.950.953.3. Place cups in cartonPlace cups in carton 0.750.75 1.001.00 1.101.104.4. Seal carton and set asideSeal carton and set aside 1.081.08 1.001.00 0.900.90

NT = NT = t t ((FF )(RF))(RF)

Determining normal time





1.1. Get two cartonsGet two cartons 0.530.53 0.500.50 1.051.052.2. Put liner in cartonPut liner in carton 0.100.10 1.001.00 0.950.953.3. Place cups in cartonPlace cups in carton 0.750.75 1.001.00 1.101.104.4. Seal carton and set asideSeal carton and set aside 1.081.08 1.001.00 0.900.90






1.1. Get two cartonsGet two cartons 0.530.53 0.500.50 1.051.05 0.280.282.2. Put liner in cartonPut liner in carton 0.100.10 1.001.00 0.950.953.3. Place cups in cartonPlace cups in carton 0.750.75 1.001.00 1.101.104.4. Seal carton and set asideSeal carton and set aside 1.081.08 1.001.00 0.900.90

NT = 0.53(0.50)(1.05) = 0.28 minuteNT = 0.53(0.50)(1.05) = 0.28 minute





1.1. Get two cartonsGet two cartons 0.530.53 0.500.50 1.051.05 0.280.282.2. Put liner in cartonPut liner in carton 0.100.10 1.001.00 0.950.95 0.100.103.3. Place cups in cartonPlace cups in carton 0.750.75 1.001.00 1.101.104.4. Seal carton and set asideSeal carton and set aside 1.081.08 1.001.00 0.900.90






1.1. Get two cartonsGet two cartons 0.530.53 0.500.50 1.051.05 0.280.282.2. Put liner in cartonPut liner in carton 0.100.10 1.001.00 0.950.95 0.100.103.3. Place cups in cartonPlace cups in carton 0.750.75 1.001.00 1.101.10 0.830.834.4. Seal carton and set asideSeal carton and set aside 1.081.08 1.001.00 0.900.90






1.1. Get two cartonsGet two cartons 0.530.53 0.500.50 1.051.05 0.280.282.2. Put liner in cartonPut liner in carton 0.100.10 1.001.00 0.950.95 0.100.103.3. Place cups in cartonPlace cups in carton 0.750.75 1.001.00 1.101.10 0.830.834.4. Seal carton and set asideSeal carton and set aside 1.081.08 1.001.00 0.900.90 0.970.97







TotalTotal 2.182.18

NT = NT = t t ((FF )(RF) NTC = )(RF) NTC = NTNT



Step 4: Setting the Standard Step 4: Setting the Standard (after 48 additional observations)(after 48 additional observations)



TotalTotal 2.182.18

ST = NTC (1 + ST = NTC (1 + AA) ) AA = allowance time added to = allowance time added to adjust for certain factorsadjust for certain factors

Determining the standard time






Allowance (Allowance (AA) = 15%) = 15% TotalTotal 2.182.18

ST = 2.18 (1 + 0.15) = 2.51 minutes/cartonST = 2.18 (1 + 0.15) = 2.51 minutes/carton






Allowance (Allowance (AA) = 15%) = 15% TotalTotal 2.182.18Standard TimeStandard Time 2.512.51



Step 4: Setting the Standard Step 4: Setting the Standard (after 48 additional observations)(after 48 additional observations)



Allowance (Allowance (AA) = 15%) = 15% TotalTotal 2.182.18Standard TimeStandard Time 2.512.51

480 minutes/day480 minutes/day2.51 minutes/carton2.51 minutes/carton

= 191 cartons/day= 191 cartons/day



Calculating Select TimeApplication H.1

Lucy and Ethel have repetitive jobs at the candy factory. Management desires to establish a time standard for this work for which they can be 95% confident to be within ± 6% of the true mean. There are three work elements involved.Step 1: Selecting work elements. #1: Pick up wrapper paper and wrap one piece of candy. #2: Put candy in a box, one at a time. #3: When the box is full (4 pieces), close it and place on conveyor.Step 2: Timing the elements. Select an average trained worker: Lucy will suffice.

* Lucy had some rare and unusual difficulties; don't use this observation.


Determining Sample SizeApplication H.1

p = 0.06 z = 1.96


Setting the Standard Application H.1

Determining Normal Time

NTC = NT = 0.12 + 0.09 + 0.06 = 0.27 minutesA = 18.5%

ST = NTC(1 + A) = 0.27(1 + 0.185) = 0.32 minutes


Data Approaches

The elemental data approach is a type of data used by analysts to derive standards when a high degree of similarity exists in the work elements.

The predetermined data approach eliminates the need for time studies. Step 1: Break each work element into its basic micromotions:

reach, move, disengage, apply pressure, grasp, position, release, and turn.

Step 2: Find the tabular value accounting for factors such as weight, distance, size of object, degree of difficulty, for each micromotion.

Step 3: Add the NT for each motion to get the NT for the job. Step 4: Adjust the normal time for allowances to give ST.

Methods time measurement (MTM) is the most commonly used system.


MTM Predetermined Data

Time TMU Wt. AllowanceDistance Hand in StaticMoved Motion Wt. (lb) Dynamic Constant

(in.) A B C B Up to Factor (TMU)3/4 or less 2.0 2.0 2.0 1.7

1 2.5 2.9 3.4 2.3 2.5 1.00 02 3.6 4.6 5.2 2.93 4.9 5.7 6.7 3.6 7.5 1.06 2.24 6.1 6.9 8.0 4.35 7.3 8.0 9.2 5.0 12.5 1.11 3.96 8.1 8.9 10.3 5.77 8.9 9.7 11.1 6.5 17.5 1.17 5.68 9.7 10.6 11.8 7.29 10.5 11.5 12.7 7.9 22.5 1.22 7.4


MTM Predetermined Data

Time TMU Wt. AllowanceDistance Hand in StaticMoved Motion Wt. (lb) Dynamic Constant

(in.) A B C B Up to Factor (TMU)3/4 or less 2.0 2.0 2.0 1.7

1 2.5 2.9 3.4 2.3 2.5 1.00 02 3.6 4.6 5.2 2.93 4.9 5.7 6.7 3.6 7.5 1.06 2.24 6.1 6.9 8.0 4.35 7.3 8.0 9.2 5.0 12.5 1.11 3.96 8.1 8.9 10.3 5.77 8.9 9.7 11.1 6.5 17.5 1.17 5.68 9.7 10.6 11.8 7.29 10.5 11.5 12.7 7.9 22.5 1.22 7.4

Case and DescriptionA Move object to other

hand or against stop.B Move object to

approximate or indefinite location.

C Move object to exact location.


The Work Sampling Method

Work sampling is the process of estimating the proportions of the time spent by people and machines on activities, based on a large number of observations. Step 1: Define the activities. Step 2: Design the observation form. Step 3: Determine the length of the study. Step 4: Determine the initial sample size. Step 5: Select random observation times. Step 6: Determine the observer schedule. Step 7: Observe the activities and record the data. Step 8: Decide whether additional sampling is required.


Work Sampling Work Sampling Example H.4Example H.4

Nurses Accessing Records


Determining the Sample Size Determining the Sample Size

Confidence interval

Probability that trueproportion will fall

within confidence interval

pp – – ee^̂ pp + + ee^̂pp̂̂

ee = = zz pp(1 – (1 – pp))nn

^ ^ ^ ^



Determining the Sample Size Determining the Sample Size Time spent accessing recordsRN 0.20LVN 0.05Maximum error ±0.03Confidence level 95%

nn = = pp(1 – (1 – pp))^ ^ ^ ^z z 22

ee



Determining the Sample SizeDetermining the Sample Size Time spent accessing recordsRN 0.20LVN 0.05Maximum error ±0.03Confidence level 95%

nn = (0.20)(0.80) = (0.20)(0.80)1.96 1.96 22

0.030.03




nn = 683 observations of RNs = 683 observations of RNs




nn = 683 observations of RNs = 683 observations of RNsnn = 203 observations of LVNs = 203 observations of LVNs



Recording the ObservationsRecording the Observations

Activity

Accessing Attending to Other support Idle or Totalrecords patients activities break observations

RN

LVN




Activity


RN

LVN

|| || ||| |

||| |




Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344



Determining Actual ProportionsDetermining Actual Proportions

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344

Actual proportion for RNs = Actual proportion for RNs = Actual proportion for LVNs = Actual proportion for LVNs =



Determining Actual ProportionsDetermining Actual Proportions

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344

Actual proportion for RNs = 124 / 688Actual proportion for RNs = 124 / 688Actual proportion for LVNs = Actual proportion for LVNs =



Determining Actual Proportions Determining Actual Proportions

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344

Actual proportion for RNs = 124 / 688Actual proportion for RNs = 124 / 688Actual proportion for LVNs = 28 / 344Actual proportion for LVNs = 28 / 344



Determining Actual Proportions Determining Actual Proportions

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344

Actual proportion for RNs = 0.18Actual proportion for RNs = 0.18Actual proportion for LVNs = 0.08Actual proportion for LVNs = 0.08



Verifying Sample SizesVerifying Sample Sizes

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344


Time spent accessing recordsRN 0.20LVN 0.05Maximum error ±0.03Confidence level 95%



Verifying Sample SizesVerifying Sample Sizes

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344



WORK TOTAL ACTIVITY PROPORTION CONFIDENCE INTERVAL REQUIREDGROUP OBS. OBS. OF TOTAL LOWER UPPER SAMPLE SIZE

RN 688 124 0.1802 0.15151 0.2090 631LVN 344 28 0.0814 0.05250 0.1103 320



Use the Results—Automate?Use the Results—Automate?

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344



RN 688 124 0.1802 0.15151 0.2090 631LVN 344 28 0.0814 0.05250 0.1103 320




Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344


Net savings = 0.25[($3,628,000)(0.18) + ($2,375,000)(0.08)] – $150,000Net savings = 0.25[($3,628,000)(0.18) + ($2,375,000)(0.08)] – $150,000


RN 688 124 0.1802 0.15151 0.2090 631LVN 344 28 0.0814 0.05250 0.1103 320




Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344


Net savings = $60,760Net savings = $60,760


RN 688 124 0.1802 0.15151 0.2090 631LVN 344 28 0.0814 0.05250 0.1103 320



Use the Results - Automate?Use the Results - Automate?

Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344


Net savings = $60,760Net savings = $60,760Net savings = 0.25[($3,628,000)(0.15) + ($2,375,000)(0.05)] – $150,000Net savings = 0.25[($3,628,000)(0.15) + ($2,375,000)(0.05)] – $150,000


RN 688 124 0.1802 0.15151 0.2090 631LVN 344 28 0.0814 0.05250 0.1103 320




Activity


RN 124 258 223 83 688

LVN 28 251 46 19 344


Net savings = $60,760Net savings = $60,760Net savings = $15,737Net savings = $15,737


RN 688 124 0.1802 0.15151 0.2090 631LVN 344 28 0.0814 0.05250 0.1103 320



Work Sampling MethodApplication H.2

Major League Baseball (MLB) is concerned about excessive game duration. Batters now spend a lot of time between pitches when they leave the box to check signals with coaches, and then go through a lengthy routine including stretching and a variety of other actions. Pitching routines are similarly elaborate. In order to speed up the game, it has been proposed toprohibit batters from leaving the box and prohibit pitchers from leaving the mound after called balls and strikes. MLB estimates the proportion of time spent in these delays to be 20% of the total game time. Before they institute a rules change, MLB would like to be 95% confident that the result of a study will show a proportion of time wasted that is accurate within ±4% of the true proportion.


Observation Form for MLBApplication H.2


Recorded Data for MLB Application H.2

0.12


Sample Size for MLBApplication H.2

(0.12)(1 – 0.12)


Managerial Considerations

Total quality management These techniques can be used in the spirit

of continuous improvement (provided management earns cooperation of labor).

Increased automation There is less need to observe and rate

worker performance, because work is machine paced.

Work sampling may be electronically monitored.


Solved Problem 1Health Insurance Claims

Selecting Work ElementsSelecting Work Elements

Operation: Insurance claim processing Date: 10/07 Observer: Jennifer Johnson

Work Element

1. Check form completion and signatures

2. Enter claim amounts, check math

3. Determine proportion of claim to be disallowed

4. Generate form letter, enter data for check

Observations1 2 3 4 5 t RF

t

r

t

r

t

r

t

r


Timing the ElementsTiming the Elements


Work Element






t

r 0.50 3.30 5.70 8.20 10.85

t

r 0.70 3.45 5.95 8.55 11.10

t

r 1.45 4.05 6.50 9.25 11.75

t

r 2.75 5.25 7.60 10.35 13.05





Work Element






t

r 0.50 3.30 5.70 8.20 10.85

t

r 0.70 3.45 5.95 8.55 11.10

t

r 1.45 4.05 6.50 9.25 11.75

t

r 2.75 5.25 7.60 10.35 13.05

t = 0.50 – 0.00

Finding the observed time





Work Element






t 0.50

r 0.50 3.30 5.70 8.20 10.85

t

r 0.70 3.45 5.95 8.55 11.10

t

r 1.45 4.05 6.50 9.25 11.75

t

r 2.75 5.25 7.60 10.35 13.05

t = 0.50






Work Element






t 0.50

r 0.50 3.30 5.70 8.20 10.85

t

r 0.70 3.45 5.95 8.55 11.10

t

r 1.45 4.05 6.50 9.25 11.75

t

r 2.75 5.25 7.60 10.35 13.05

t = 0.70 – 0.50






Work Element






t 0.50

r 0.50 3.30 5.70 8.20 10.85

t 0.20

r 0.70 3.45 5.95 8.55 11.10

t 0.75

r 1.45 4.05 6.50 9.25 11.75

t 1.30

r 2.75 5.25 7.60 10.35 13.05






Work Element






t 0.50

r 0.50 3.30 5.70 8.20 10.85

t 0.20

r 0.70 3.45 5.95 8.55 11.10

t 0.75

r 1.45 4.05 6.50 9.25 11.75

t 1.30

r 2.75 5.25 7.60 10.35 13.05

t = 3.30 – 2.75





Work Element






t 0.50 0.55

r 0.50 3.30 5.70 8.20 10.85

t 0.20

r 0.70 3.45 5.95 8.55 11.10

t 0.75

r 1.45 4.05 6.50 9.25 11.75

t 1.30

r 2.75 5.25 7.60 10.35 13.05





Work Element






t 0.50 0.55 0.45 0.60 0.50

r 0.50 3.30 5.70 8.20 10.85

t 0.20 0.15 0.25 0.35 0.25

r 0.70 3.45 5.95 8.55 11.10

t 0.75 0.60 0.55 0.70 0.65

r 1.45 4.05 6.50 9.25 11.75

t 1.30 1.20 1.10 1.10 1.30

r 2.75 5.25 7.60 10.35 13.05





Work Element






t 0.50 0.55 0.45 0.60 0.50 0.52 1.1 0.0570

r 0.50 3.30 5.70 8.20 10.85

t 0.20 0.15 0.25 0.35 0.25 0.24 1.2 0.0742

r 0.70 3.45 5.95 8.55 11.10

t 0.75 0.60 0.55 0.70 0.65 0.65 1.2 0.0791

r 1.45 4.05 6.50 9.25 11.75

t 1.30 1.20 1.10 1.10 1.30 1.20 0.9 0.1000

r 2.75 5.25 7.60 10.35 13.05



measuring output rates

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