Chapter 10 work measurements and standards

Work Measurement & Standards

Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD

Micro-Approach School of Job DesignMicro-Approach School of Job Design

In 1820s England, the first efforts to cut costs and increase productivity began.

Frederick Winslow Taylor ( 1881 ) organized the research findings and developed more formal methods.

He is considered to be the Father of Scientific Management.

THE TAYLOR SCHOOL / THE TECHNICAL - PHYSICAL SCHOOL

Taylor School of Job Design

• Eliminate idle time for workers and machines.

• Eliminate duplication of effort.

• Streamline the flow of work through the firm.

• Rearrange task sequences for more efficiency.

• Reduce jobs to short-cycle , repetitive ones for higher productivity and eventual replacement of humans with machines.

• Systematic reduction of skill requirements in each job.

ASSUMES WORKERS SOLE MOTIVATION IS MORE MONEY

TENETS

Work Measurement & TimeWork Measurement & TimeStandardsStandards

Direct Time Study

Predetermined Time Study

Work Sampling

Performance Ratings Allowance Factors Sample Size Determination

Observation Schedules Interpretation of Findings Sample Size Determination

Therbligs The MTM Product

Direct Time StudyDirect Time StudyEXAMPLE

Problem Statement

Twenty workers who perform the identical job are selected forthis time study. Each worker will be timed over five (5) cycles.Assume that the total observed time will eventually equal 400 minutes.

Requirement

Develop a time standard for a particular worker.

THE WORKER SAMPLE CAN BESELECTED FROM A SINGLE FACILITY

OR IT MAY BE A COMPOSITE SAMPLE SELECTED FROM

SEVERAL FACILITIES


1. COMPUTE THE OBSERVED TIME

OT = SUM OF ALL OBSERVED TIMES

NUMBER OF OBSERVED CYCLES

= 400 MINUTES

100 CYCLES= 4.000 MINUTES

OBSERVED TIME IS COMPUTED THREE PLACES TO THE RIGHT OF THE DECIMAL POINT

akaAverage

CycleTime


2. COMPUTE THE NORMAL TIME

NT = OT x PR

THE PERFORMANCE RATING ADJUSTS THE OBSERVED TIME TO WHAT THE NORMAL TIMESHOULD BE FOR A PARTICULAR WORKER.

EVERY WORKER IS ASSIGNED A UNIQUE PERFORMANCE RATING BY THE TIME AND MOTIONANALYST.

*

Performance RatingsPerformance Ratings

PR = 1.0 denotes an average worker.

PR < 1.0 denotes a fast worker.

PR > 1.0 denotes a slow worker.

PERFORMANCE RATINGS ARE ESTABLISHED FOR EACH WORKER.IT IS STILL SOMETHING OF AN ART AND CONSEQUENTLY CAN BE

CHALLENGED BY UNION OFFICIALS. THOROUGH DOCUMENTATION OF ALL PERFORMANCE RATINGS IS ESSENTIAL.

Direct Time StudyDirect Time Study

2. NORMAL TIME ( continued )

A particular worker in this time study has been assigned a performance rating of 85% .

This means s/he has been judged to be a fast worker and thus should be held to a bit shorter normal time , or higher level of performance.

NT = ( 4.000 ) x ( .85 ) = 3.400 MINUTES


3. COMPUTE THE STANDARD TIME

ST = NT

1 - AFNT + [ AF x OT ]

**

* THE ALLOWANCE FACTOR IS ASSIGNED TO ALL WORKERS PERFORMING THEIDENTICAL TASK. IT INCLUDES EXTRA TIME FOR PERSONAL NEEDS, FATIGUE,

RECURRING AND UNAVOIDABLE WORK DELAYS, AND CLEANUP BETWEENVARIOUS OPERATIONS

Allowance FactorsAllowance Factors

Constant Allowances PERSONAL……………5%

FATIGUE……………....4%

Variable Allowances STANDING………….2 to 4%

MENTAL STRAIN….4 to 8%

TEDIOUSNESS…….2 to 5%

NOISE LEVEL……...2 to 5%

HEAT / HUMIDITY…0 to 10%

POOR LIGHTING…..2 to 5%

EXAMPLE

Direct Time StDirect Time StudyudyEXAMPLE

ASSUME AN ALLOWANCE FACTOR OF 13% WITH THE CHOICE OF FORMULA LEFT TO THE DISCRETION OF THE ANALYST.

3. COMPUTE THE STANDARD TIME ( continued )

ST = 3.400

1 - .13=

3.400

.87= 3.900 MINUTES

ST = 3.400 + [.13 x 4.000] = 3.400 + .5200 = 3.920 MINUTES

QM for WINDOWSQM for WINDOWS

Work MeasurementWork Measurementandand

Standard SettingStandard Setting

For simplicity, we assume that each of the five workers observed had an actual performance time of 4 minutes

The particular worker that we are setting a standardfor, has a performance rating of 85%

This worker performs a short cycle job with onlyone (1) particular activity or element involved

Average cycle time or OT ( observed time ) = 4.0 minutes

Normal time ( OT x PR ) = ( 4.00 x .85 ) = 3.4 minutes

Standard time = [ NT / ( 1 - AF ) ] = [ 3.4 / ( 1 - .13 ) ] = 3.91 minutes

Direct Time StudyDirect Time StudySAMPLE SIZE DETERMINATION

Suppose we want to know the number of cycles we must observe in order to obtainan average cycle time that is 95% certain to fall within +/- 5% of the actual averagecycle time for all workers performing thisjob or task within a job.

μ


Let’s say you did a pilot time study in whichsix workers performing the identical job ortask were observed over two cycles each

for a total of twelve cycles

Average cycle time for this sample turnedout to be 3.000 minutes with a standard

deviation of 1.000 minute

x = 3.000

s = 1.000

_


SAMPLE SIZE

DETERMINATION

THE FORMULA

n = z s

x

2

where:

x = THE SAMPLE MEANs = THE SAMPLE STANDARD DEVIATIONε = ALLOWABLE OR TOLERATED ERROR EXPRESSED AS A DECIMAL ( 5% = .05 )z = NUMBER OF STANDARD DEVIATIONS FOR THE DESIRED CONFIDENCE LEVEL ( 95% = 1.96 )

ε_


n = 1.96 x 1.0

2

.05 x 3.0

=1.96

.15

2

13.06

2

=

171≈


Sample SizeDetermination


ADDITIONAL COMMENTS

When observed times are not consistent, they need to be reviewed. Abnormally short or long times may be the result of an observational error and are usually discarded.

Normal times (NT) are sometimes computed for each element of a job because the performance rating may vary for each element. In other words, the same worker may be fast on some tasks but slow or average on other tasks.

Intra - Job Performance RatingsIntra - Job Performance Ratings

EXAMPLE

Job Element Performance Rating

Drawing Materials 0.99

Assembling Parts 1.08

Product Coating 0.83

Product Inspection 1.20

A MUCH MORE ACCURATESTANDARD SETTING

PROCEDURE !

Predetermined Time StandardsPredetermined Time Standards

• Routine, repetitive jobs are divided into basic motions

of the human body.

• These motions have been studied under numerous conditions and assigned specific times.

• A time standard for a particular job is found by adding these basic motion times together.

Predetermined Time StandardsPredetermined Time StandardsTHERBLIGS

Basic or elemental motions of the human body are called therbligs

Term was coined by Frank Gilbreth

They include such activities as select, grasp, position, assemble, reach, hold, and inspect

Time values for therbligs are specified in very detailed tables

*

GILBRETH SPELLED BACKWARDS WITH “T” AND “H” TRANSPOSED

Predetermined Time StandardsPredetermined Time StandardsTHERBLIGS: ELEMENTAL MOTIONS OF THE HUMAN BODY

KNEESKNEES

HEADHEAD

ARMSARMS

TORSOTORSO

LEGSLEGS

ELBOWSELBOWS

FEETFEET

ONE OF THE FIRST JOBS STUDIED WAS THAT OF THE STOKERONE OF THE FIRST JOBS STUDIED WAS THAT OF THE STOKER

Frank & Lillian Gilbreth Colleagues of Frederick Taylor

Among the first to systematically seek the best way to perform jobs

They used clocks, still cameras, and movie cameras to record the movements of workers while they performed their jobs

Their family was the basis for the movie “Cheaper by the Dozen”.

1950&

1995

The Gilbreth Family

PHOTOGRAPH TAKEN AT THEIR MONTCLAIR, NEW JERSEY HOMEPHOTOGRAPH TAKEN AT THEIR MONTCLAIR, NEW JERSEY HOME

Predetermined Time StandardsPredetermined Time StandardsTHERBLIG TIME MEASUREMENT

Stated in terms of time measurement units or TMUs

One TMU equals .00001 hours

One TMU equals .0006 minutes

There are 100,000 TMUs in one hour

Predetermined Time StandardsPredetermined Time Standards

• Methods Time Measurement is a product of the MTM

Association, Fairlawn, New Jersey 07410.

• It is a family of products including MTM-C which deals with clerical tasks, and MTM-HC which deals with healthcare industry tasks.

• Provides a comprehensive system of predetermined time standards which would be prohibitively expensive for a single firm to develop.

• Services include consulting, data base rental, and custom performance standards for one or more jobs set by MTM professional staff.

MTM ASSOCIATION

MTM IS A COPYRIGHTED PRODUCT

Predetermined Time StudyPredetermined Time StudyUSING THE MTM SYSTEM TO DEVELOP A TIME

The most complex motion or therbligin the MTM system is get and place .

We must know four things:

1. What is to be gotten.2. Its approximate weight.3. Where it must be placed.4. How far it must be moved.

Predetermined Time StudyPredetermined Time StudyDEVELOPING A TIME FOR GET AND PLACE

The conditions for getting a unit and placing it before the worker are:

1. A part is needed for assembly.2. Its weight is less than 2 pounds.3. It must be moved to the worker’s immediate front.4. It must be moved between 8 and 20 inches from the far corner of a work table.

Predetermined Time Study

Each Part

< 2 lbs

WorkBench

StandingWorker

8 t

o 2

0 in

ches

8 to

20

inch

es

“ GET AND PLACE ” EXAMPLE

Predetermined Time StudyPredetermined Time StudySAMPLE MTM TABLE FOR “GET” AND “PLACE”

DistanceDistanceIn In

InchesInches< 8< 8 > 8> 8

< 20< 20> 20> 20< 32< 32

WeightWeight ( lbs. )( lbs. )

“ GET ” Conditions

“ “ PLACE ”PLACE ”AccuracyAccuracy

Code 1 2 3

Approx AA 20 35 50

<2 lbs.<2 lbs. EASY LooseLoose AB 30 45 60

TightTight AC 40 55 70

THEREFORE MTM TIME FOR THIS THERBLIG IS 35 TMUs AND ITS CODE No. IS AA2

PredeterminPredetermined Time Studyed Time StudyDEVELOPING A TIME FOR GET AND PLACE

Additional Weight Categories ( not shown )

> 2 pounds < 18 pounds

> 18 pounds < 45 pounds

Additional Conditions of “Get” ( not shown )

Difficult

Handful

OF COURSE THE MTM THERBLIGS FOR THESE CONDITIONS WOULD HAVE DIFFERENT CODES SUCH AS AD2, AE3

Predetermined Time StudyPredetermined Time StudyCOMPLETE MTM JOB TIME EXAMPLE

JOB ELEMENT( THERBLIG )

JOB ELEMENT

CODE

JOB ELEMENT TIME( in TMUs )

Draw item “A” from left corner of table

35

Draw item “B” from

right corner of table55

45

83

40

∑ TMUs 258

Assemble the two Items

Inspect the assembly

Place the assemblyin a box

AA2

AC2

AD2

PT1

GB3

.0006 x 258 = .1548 STANDARD MINUTES FOR THIS COMPLETE JOB

Predetermined Time StudyPredetermined Time Study2nd EXAMPLE

Suppose there are 8 therbligs in a short-cycle, repetitive job

Suppose the sum of the therblig TMUs = 397.9

Since each TMU = .036 seconds, this job’s cycle time equals 14.32 seconds ( 397.9 x .036 )

14.32 seconds = .23838 minutes ( 14.32 / 60 )

251.7 cycles of this job should be expected each hour by management ( 60 / .23838 )

Standard hourly output would therefore be 252 units

Predetermined Time StudyPredetermined Time Study

Does not disrupt the actual production operation.

No performance ratings are necessary.

No allowance factors are necessary.

Unions tend to accept it as fair.

Particularly effective in firms that employ many workers performing similar tasks, i.e.

it is cost-effective.

Can be used for planning purposes because the time standard can be set before the job actually exists!

ADVANTAGES

Work SamplingWork Sampling

o Developed in England in the 1930s by Leonard Tippet

o Estimates the percentage of time that a worker spends on various tasks.

o Random observations are used to record employee activity.

o The only technique available for measuring and evaluating non-repetitive jobs.

The Most UsedThe Most UsedTechnique in theTechnique in theService SectorService Sector

Leonard Henry Caleb TippettLeonard Henry Caleb Tippett1902 - 19851902 - 1985

English physicist and statisticianwho used what he called a

“snap reading method” to obtain,at random time intervals, observations

of textile machine operators forthe purpose of estimating the

percentage of time spent on theirduties.

L.H.C. Tippett

Leonard Henry Caleb TippettLeonard Henry Caleb Tippett

Awarded the Walter Shewart Medal of the American Society for Quality Control

Awarded the Warner Medal of the Textile Institute for improving the production efficiency and operative utilization of the textile industry

Educated at Imperial College, and University College, London

President of the Royal Statistical Society, 1965

Shirley Institute, Manchester, England, 1925-1965

1902 - 1985

Work Sampling ApplicationsWork Sampling Applications

Establishing labor and production standards.

Discovering how employees allocate their time for both work and non-work activity.

Providing the basis for staffing changes, job training, reassignments of duties, hiring, and termination.

Work Sampling In ActionWork Sampling In Action

The mail order catalogerLand’s End expects its

call center representativesto be busy 85% of the time

When the “busy” ratio hits90% , the firm believes it is

not attaining its set goalof high quality service

The firm then plansto hire more

representativesto restore the desired

level of service


Monday 10:30 am Flying paper airplanes

Wednesday 2:20 pm Watching TV

Thursday 9:45 am Reading Sports Page

Thursday 1:25 pm Buying Cruise Tickets On-Line

Friday 2:30 pm Doing Homework for Night School

Friday 4:30 pm Left Early

SIX RANDOM VISITS TO JOE’S OFFICE

JOEJOE

BOSSBOSS

EXPECT TOSEE THIS

ANDMORE !

Work Sampling ProcedureWork Sampling Procedure

I. Take a preliminary sample to obtain an estimate of a parameter value such as the percentage of time a worker is busy.

II. Compute the sample size required for the formal work sampling study.

III. Prepare a worker observation schedule.

IV. Observe and record worker activities.

V. Determine how workers are spending their time.

Work Sampling ExampleWork Sampling ExampleThe REGISTRY

of MOTOR VEHICLES

The manager of a branch officeestimates that her employeesare idle 25% of the time. Shewants to confirm or disprove this by taking a work sample

that is accurate to within +/- 3% and yields a 95% confidence

Sample SizeSample Size CoComputation Formulamputation Formula

z x p x q2

ε 2

where:

n = required sample size

z = standard normal deviate for the desired confidence level

p = estimated value of the sample proportion ( of time worker is “busy” )

q = estimated value of the sample proportion ( of time worker is “idle” )

ε = acceptable error level ( in percent )

n =

Sample Size ComputationSample Size Computation

n = (2) x (.25)(.75)

(.03)= 833

2

2

95% CONFIDENCE LEVEL ( z ) 3 PERCENT TOLERATED ERROR ( ε )

75% BUSY PROPORTION ( q )25% IDLE PROPORTION ( p )

WORK SAMPLING

WE COULD HAVE DESIGNATED THE “BUSY” PROPORTION “p” AND THE “IDLE” PROPORTION “q”

Work Sampling ExampleWork Sampling ExampleThe REGISTRY

of MOTOR VEHICLES

Utilizing the sample size formula,she finds that 833 observations

should be taken. If the percentageof idle time observed is not closeto 25% as the study progresses,the number of observations may

need to be recomputed and raisedas appropriate.



Work Sampling ResultsWork Sampling ResultsThe REGISTRY of MOTOR VEHICLES

Number of Observations Activity

485 on phone / meeting clients

126 idle

62 personal time

23 supervisor meetings

137 filing, data entry

∑ = 833NOT

WORKRELATED

Work Sampling ConclusionWork Sampling ConclusionThe REGISTRY of MOTOR VEHICLES

All but 188 of the observations are work-related.

Since 22.6% is less idle time than the branch manager believes necessary to ensure a high client service level, she needs to find a way to reduce current work loads.

This could be accomplished via a reassignment of duties or the hiring of additional personnel.

( 126 IDLE & 62 PERSONAL )

( 188 / 833 = 22% )

Employee Observation ScheduleEmployee Observation SchedulePREPARATION

EXAMPLE

Draw five random numbers from a table:

07 12 22 25 49

These random numbers can then be usedto create an observation schedule:

9:07 9:12 9:22 9:25 9:49

RANDOM NUMBERS ARE USED TO GENERATE THE VISITATION SCHEDULE

9:07 - JOE

9:12 - BOB

9:22 - CAROL

9:25 - TIM

9:49 - JOAN

Employee Observation ScheduleEmployee Observation Schedule

COMMENTS

Observations are to be made in a non-intrusive manner so as not to distort employee normal work patterns.

Observations are to be made in a random and unbiased manner over a period of 2 weeks in order to ensure a valid sample.

Activities that constitute “work” must be clearly defined such as filing, data entry, meetings, and writing reports.

Work Sampling ResultsWork Sampling ResultsTYPICAL MANUFACTURING SITUATION

PRODUCTIVE WORK………………………75%IDLE TIME BETWEEN TASKS……………..9%BREAKS AND LUNCH………………………7%DOWNTIME & UNSCHEDULED TASKS….4%CLEANUP…………………………………......3%START- UP…………………………………….2%


• LESS EXPENSIVE

• NO TIMING DEVICES

• LITTLE TRAINING NEEDED

• STUDY CAN BE DELAYED TEMPORARILY WITH LITTLE IMPACT ON THE RESULTS

• WORKER HAS LITTLE CHANCE OF AFFECTING THE OUTCOME

• LESS LIKELY TO GENERATE EMPLOYEE OBJECTIONS

ADVANTAGES


• IT DOES NOT DIVIDE WORK ELEMENTS (THERBLIGS) AS THOROUGHLY AS FORMAL TIME STUDIES

• IT CAN YIELD INCORRECT / BIASED RESULTS IF THE OBSERVER DOES NOT CONFORM TO RANDOM ROUTES OF TRAVEL AND RANDOM OBSERVATION

• IT TENDS TO BE LESS ACCURATE WHEN CYCLE TIMES ARE SHORT

DISADVANTAGES

Work Measurement & Standards

Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2011 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2011 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD

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Chapter 10 work measurements and standards