Chapter 10 work measurements and standards

Work Measurement & Standards

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

Micro-Approach School of Job Design
THE TAYLOR SCHOOL / THE TECHNICAL - PHYSICAL SCHOOL

 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.

Taylor School of Job Design
TENETS

• Eliminate idle time for workers • Reduce jobs to short-cycle ,
and machines. repetitive ones for higher
productivity and eventual
• replacement of humans with
Eliminate duplication of effort.
machines.

• Streamline the flow of work
• Systematic reduction of skill
through the firm.
requirements in each job.

• Rearrange task sequences for
more efficiency.

ASSUMES WORKERS SOLE MOTIVATION IS MORE MONEY

Work Measurement & Time
Standards
 Direct Time Study
 Performance Ratings
 Allowance Factors
 Sample Size Determination

 Predetermined Time
Study
 Therbligs
 The MTM Product

 Work Sampling
 Observation Schedules
 Interpretation of Findings
 Sample Size Determination

Direct Time Study
EXAMPLE THE WORKER SAMPLE CAN BE
SELECTED FROM A SINGLE FACILITY
OR IT MAY BE A COMPOSITE
SAMPLE SELECTED FROM
SEVERAL FACILITIES

Problem Statement

Twenty workers who perform the identical job are selected for
this 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.

Direct Time Study
EXAMPLE

aka
Average
1. COMPUTE THE OBSERVED TIME Cycle
Time

SUM OF ALL OBSERVED TIMES
OT =
NUMBER OF OBSERVED CYCLES

400 MINUTES
= = 4.000 MINUTES
100 CYCLES

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

Direct Time Study
EXAMPLE

2. COMPUTE THE NORMAL TIME

NT = OT x PR *

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

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

Performance Ratings
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.

 PR = 1.0 denotes an average worker.
 PR < 1.0 denotes a fast worker.

 PR > 1.0 denotes a slow worker.

Direct 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

Direct Time Study
EXAMPLE

3. COMPUTE THE STANDARD TIME

NT
ST = NT + [ AF*x OT ]
1 - AF*

* THE ALLOWANCE FACTOR IS ASSIGNED TO ALL WORKERS PERFORMING THE
IDENTICAL TASK. IT INCLUDES EXTRA TIME FOR PERSONAL NEEDS, FATIGUE,
RECURRING AND UNAVOIDABLE WORK DELAYS, AND CLEANUP BETWEEN
VARIOUS OPERATIONS

Allowance Factors
EXAMPLE

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%

Direct Time Study
EXAMPLE

3. COMPUTE THE STANDARD TIME ( continued )

3.400 3.400
ST = = = 3.900 MINUTES
1 - .13 .87

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

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

QM for WINDOWS

Work Measurement
and
Standard Setting

Chapter 10 work measurements and standards

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 standard
for, has a performance rating of 85%

This worker performs a short cycle job with only
one (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 Study
SAMPLE SIZE DETERMINATION

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

μ

Direct Time Study

Let’s say you did a pilot time study in which
six workers performing the identical job or
task were observed over two cycles each _
for a total of twelve cycles x = 3.000
s = 1.000
Average cycle time for this sample turned
out to be 3.000 minutes with a standard
deviation of 1.000 minute

Direct Time Study

THE FORMULA 2
zs
n = _
εx
where:
x = THE SAMPLE MEAN
s = THE SAMPLE STANDARD DEVIATION
ε = ALLOWABLE OR TOLERATED ERROR
EXPRESSED AS A DECIMAL ( 5% = .05 )
z = NUMBER OF STANDARD DEVIATIONS
FOR THE DESIRED CONFIDENCE LEVEL
( 95% = 1.96 )

SAMPLE
SIZE
DETERMINATION

Direct Time Study

2
1.96 x 1.0
n = .05 x 3.0
2
1.96
= .15
2
= 13.06

≈ 171

QM for WINDOWS

Sample Size
Determination

Direct Time Study
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 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
ACCURATE
STANDARD
SETTING
PROCEDURE !

Predetermined 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.

THERBLIGS

 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

THERBLIGS: ELEMENTAL MOTIONS OF THE HUMAN BODY

KNEES
HEAD
ARMS
TORSO
LEGS
ELBOWS
FEET

ONE 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 HOME

THERBLIG 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

MTM ASSOCIATION

• Methods Time Measurement • Provides a comprehensive
is a product of the MTM system of predetermined time
Association, Fairlawn, New standards which would be
Jersey 07410. prohibitively expensive for a
single firm to develop.

• Services include consulting,
• It is a family of products
data base rental, and custom
including MTM-C which deals
performance standards for one
with clerical tasks, and MTM-
or more jobs set by MTM
HC which deals with healthcare
professional staff.
industry tasks.

MTM IS A COPYRIGHTED PRODUCT

Predetermined Time Study
USING THE MTM SYSTEM TO DEVELOP A TIME

The most complex motion or therblig
in 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.

DEVELOPING 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.

“ GET AND PLACE ” EXAMPLE

Each
Part
< 2 lbs

hes
inc
20
8 to

Work Standing
Bench Worker

SAMPLE MTM TABLE FOR “GET” AND “PLACE”

Distance >8 > 20
In <8
< 20 < 32
Inches

Weight “ GET ” “ PLACE ”
Code 1 2 3
( lbs. ) Conditions Accuracy

Approx AA 20 35 50

<2 lbs. EASY Loose AB 30 45 60

Tight
AC 40 55 70

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

DEVELOPING 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

COMPLETE MTM JOB TIME EXAMPLE

JOB ELEMENT JOB ELEMENT JOB ELEMENT TIME
( THERBLIG ) ( in TMUs )
CODE
Draw item “A” from left 35
corner of table AA2
Draw item “B” from 55
right corner of table
AC2

Assemble the two Items AD2 45
Inspect the assembly PT1 83
Place the assembly
GB3
40
in a box

∑ TMUs 258

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

2nd 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

ADVANTAGES

 Does not disrupt the actual  Particularly effective in firms
production operation. that employ many workers
performing similar tasks, i.e.
 No performance ratings are it is cost-effective.
necessary.
 Can be used for planning
 No allowance factors are
necessary. purposes because the time
standard can be set before the
job actually exists!
 Unions tend to accept it as fair.

Work 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- The Most Used
repetitive jobs. Technique in the
Service Sector

Leonard Henry Caleb Tippett
1902 - 1985

English physicist and statistician
who used what he called a
“snap reading method” to obtain,
at random time intervals, observations
of textile machine operators for
the purpose of estimating the
percentage of time spent on their
duties.

L.H.C. Tippett

Leonard Henry Caleb Tippett
1902 - 1985

 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

Work 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 Action

The firm then plans
The mail order cataloger
to hire more
Land’s End expects its
representatives
call center representatives
to restore the desired
to be busy 85% of the time
level of service

When the “busy” ratio hits
90% , the firm believes it is
not attaining its set goal
of high quality service

Work Sampling
EXPECT TO
SEE THIS
AND
MORE !

SIX RANDOM VISITS TO JOE’S OFFICE

JOE
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

BOSS

Work 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 Example
The REGISTRY
of
MOTOR VEHICLES

The manager of a branch office
estimates that her employees
are idle 25% of the time. She
wants to confirm or disprove
this by taking a work sample
that is accurate to within +/- 3%
and yields a 95% confidence

Sample Size Computation Formula

2
n = z x p x q
ε2
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 )

Sample Size Computation
WORK SAMPLING

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

2
(2) x (.25)(.75)
n= = 833
2
(.03)

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

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

Work Sampling Example
The REGISTRY
of
MOTOR VEHICLES

Utilizing the sample size formula,
she finds that 833 observations
should be taken. If the percentage
of idle time observed is not close
to 25% as the study progresses,
the number of observations may
need to be recomputed and raised
as appropriate.

QM for WINDOWS

Work Sampling

Work Sampling Results
The 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

∑ = 833 NOT
WORK
RELATED

Work Sampling Conclusion
The REGISTRY of MOTOR VEHICLES

 All but 188 of the observations are work-related.
( 126 IDLE & 62 PERSONAL )

 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.
( 188 / 833 = 22% )

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

Employee Observation Schedule
PREPARATION

RANDOM NUMBERS ARE USED TO GENERATE THE VISITATION SCHEDULE

EXAMPLE
Draw five random numbers from a table:

07 12 22 25 49
These random numbers can then be used
to create an observation schedule:
OE
- J OB
7
9:0 2 - B ROL 9:07 9:12 9:22 9:25 9:49
A
9:1 2 - C M
9:2 5 - TI AN
9:2 9 - JO
9:4

Employee 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 Results
TYPICAL MANUFACTURING SITUATION

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

Work Sampling
ADVANTAGES

• 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

Work Sampling
DISADVANTAGES

• 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

Work Measurement & Standards

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

Chapter 10 work measurements and standards

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