Chapter 11
Work System Design
What to Design?
• Job design
• Work Measurement design
• Worker Compensation design
Job Design
• Job design is to specify the contents of a job
or position.
• Examples of questions to be answered in job
design:
– What is the job’s description?
– What is the purpose of the job?
– Where is the job done?
– Who does the job?
– What background, training, or skills are required
to do the job?
Feasibility Considerations of a Job
• Technical feasibility
– The job must be physically and mentally doable.
• Economic feasibility
– The cost of the job should be less than the value it
adds.
• Behavioral feasibility
– How much satisfaction an employee feels from
doing the job.
Case of Google, p.413-414
• How jobs and job environment are
designed
Machine or People?
- Should Job Be Automated?
• Considerations:
– Safety & risk of injury to workers
– Repetitive nature of the task
– Degree of precision required
– Complexity of the task
– Need for empathy, compassion, or other
emotional elements
– Need for personal customer relationships
Labor Specialization
• What is the breadth of a job.
• The higher the level of specialization, the
narrower is the employee’s scope of
expertise required.
• Although job satisfaction is associated
with many specialized professional jobs,
dissatisfaction is often associated with
specialized non-professional jobs.
Specialized Non-Professional Jobs
Management’s View
Advantages:
• Readily available labor
Disadvantages:
• High absenteeism
• Minimal training
required
• High turnover rates
• Reasonable wages costs
• Grievances filed
• High scrap rates
• High productivity
8
Specialized Non-Professional Jobs
Employee’s View
Advantages:
• Minimal credentials
required
Disadvantages:
• Boredom
• Little growth opportunity
• Minimal responsibilities • Little control over work
• Minimal mental effort
• Little room for initiative
needed
• Little intrinsic satisfaction
• Reasonable wages
9
Eliminating Employee Boredom
Enhance Employee Motivation
• Job enlargement
– Horizontal expansion of the scope of the work
assigned.
• Job enrichment
– Vertical expansion of the job through increased
worker responsibility. Example:
• Adding work planning or inspection to a routine assembly task
• Job rotation
– Shifting workers to different tasks to increase
understanding of the total process and reduce
fatigue.
Team Approaches Considered in
Job Design
• Problem-solving teams:
– For workplace problems
• Special-purpose task forces:
– For highly-focused, short-term problem
solving
• Self-directed teams:
– Integrated team approach for controlling
portions of the process.
Alternative Workplace
• Some jobs are not necessarily carried out
at the centralized work sites, office
buildings, or work shops.
• Alternative workplaces are made
possible by technologies like Internet,
email, cell phones, & video conferencing.
Method Analysis
• Method analysis is for designing the details of
how a job is done.
• The output of a Method Analysis process is a
standard operating procedure for doing the
job.
• Job design tells the positions needed in an
operation process; while method analysis tells
the details of standard procedures of how
each job is done.
Key Steps in Method Analysis
• Collecting information.
• Chart the job operation by showing the steps
involved.
• Evaluate step by step to identify the
unnecessary non-value-added activities.
• Make suggestion on procedure of doing the
job.
A Method Analysis Case
at FEAT Company (p.420-421)
• Job:
Solder wires to transformer.
• Current layout of workstation:
Fig. 11-3.
• Current procedure:
Process chart in Fig. 11-2
• How to improve the procedure?
Work Environment
• Work environment is a part of job design.
• Environment of a work place include:
temperature, humidity, ventilation,
illumination, noise, color, decoration,
supporting facilities, …
Work Measurement
• Work measurement is to determine the
time a job takes (rather than “how” to
measure a job).
• Standard time of a job is how long the
job should take.
Uses of Standard Time
• With the benchmark of standard times
for jobs, the company can
– Cost a product and price a product;
– Evaluate workers’ performance;
– Plan and schedule facilities and workers.
Methods of Setting Standard
Times
•
•
•
•
Time study
Elemental time data
Predetermined time data
Work sampling
Time Study
• Time study is to determine the standard
time of a job by actually observing the
operator.
• The operator knows he is observed for
setting the standard time.
Keys in Time Study
• Break the job into small elements that
are easy to observe.
• Calculate number of observations
required.
• Time each element.
• Summarize the results, considering
relevant human factors.
How Many Observations?
• Take a trial sample of observations (10 for
example), find out its mean X and standard
deviation s.
• Calculate minimum observations, n:
where
z s 
n

a X 
2
z= number of standard deviations for desired confidence, see Table
11-3 on p.425;
a = desired accuracy as % of mean time x , 5% for example.
Performance Rating Factor (PRF)
• PRF is an attempt to counterbalance any
unusual patterns noted in the observed work
pace, for example, deliberately working slowly
or faster.
• Average work pace: PRF=1.
• Slower than average: PRF<1.
• Faster than average: PRF>1.
Frequency of Occurrence (F)
• It indicates how often a work element must be
done in each work cycle (the process to finish
a job).
• If an element is done in every cycle, then F=1.
• If an element is done once in every N cycles,
then F=1/N.
PFD Factor
• PFD factor shows the percent of efficiency
decrease due to personal time, fatigue, or
unavoidable delays when workers continue to
work on a job for hours.
• PFD=12%, for example, indicates an estimate
that worker’s efficiency will decrease by 12%
from the normal if continuing to work on the
job for hours.
Allowance Factor (AF)
• AF is the factor taking PFD (personal time,
fatigue, and unavoidable delay) into account.
• For setting standard work times, AF is
calculated as:
1
AF 
1  PFD
Note: Discussions of AF in the textbook on p.427 are
confusing. Ignore the concept of AFjob.
Steps for Setting Standard Times
of an Element by Time Study (1)
• Run about a few (10 for example) trial
observations on the work time of the element.
Calculate the average observed time of the
element x and standard deviation s.
Steps for Setting Standard Times
of an Element by Time Study (2)
• Determine number of observations required,
2
n:
z s 
n

a
 X
where
z= number of standard deviations for desired confidence, see Table
11-3 on p.425;
a = desired accuracy as % of mean time x , 5% for example.
Steps for Setting Standard Times
of an Element by Time Study (3)
• Run more observations on the work time of
the element so that number of total
observations, including the initial trial 10,
equals to n.
• Based on the n observations, calculate the
average time which is called mean observed
time (MOT).
Steps for Setting Standard Times
of an Element by Time Study (4)
• Figure out “performance rating factor (PRF)”
of the worker who was observed in the time
study.
• Figure out “frequency of occurrence (F)” of
the element.
• Calculate normal time NT:
NT = (MOT)(PRF)(F).
Steps for Setting Standard Times
of an Element by Time Study (5)
• Figure out the “factor for personal time,
fatigue, and unavoidable delay (PFD)”.
• Calculate “allowance factor AF”:
1
AF 
1  PFD
Note: Ignore the formula AF=1+PFDgiven in book.
• Calculate “standard time ST” of the element:
ST = (NT)(AF).
Standard Time of a Job
• After finding out the standard time of
every element of a job, the standard time
of the job is the sum of the standard
times of all those elements.
Elemental Time Database
• It is the database of standard times of job
elements from previous time studies.
• If a job contains some elements that are
already stored in the database, then new
time studies for those elements are not
necessary.
• Adjustment may be needed.
Predetermined Time Database
• It is the published database of elemental
times.
• It is used for setting the job time without
doing new time studies.
• One TMU (time measurement unit) equals to
0.0006 minute or 0.036 seconds.
• Example: p.430
Work Sampling
• Working sampling is technique for setting
the proportion of time a worker spends
on a particular activity.
• Compared to time study, work sampling
does not time the activity; instead, it
makes a bunch of random observations
to identify the percent of time the
worker is doing the activity.
How Many Observations?
• Take a trial sample of observations (30 for
example), find out proportion p of doing the
activity in this sample.
• Calculate minimum observations, n:
2
where
z
n    p(1  p)
e
z= number of standard deviations for desired confidence, see Table
11-3 on p.425;
e = desired accuracy as % of true proportion, 3% for example.
Steps of Doing Work Sampling
• Run 30 trial observations.
p = (number of times doing the activity) / 30.
• Calculate number of observations:
2
z
n    p(1  p)
e
• Run (n-30) more observations.
• Calculate p based on n observations
p = (number of times doing the activity) / n.
To Know Time Spent on an Activity
• Two ways to get the information about a
worker’s time spent on an activity among
some other activities:
– Direct observation as in time study;
– Random checking as in work sampling.
• These are also two ways of evaluating
work pace and efficiency in
management.
Compensation
• Time-based system
• Output-based system
• Group incentive plan
– Profit sharing
– Gain sharing (sharing the saved cost)
• Individual incentive or group incentive?
Learning Curve
n
log2x
• Tx = T1 * L = T1 * L
• where Tx=time required to do the job for the x-th time,
T1=time required to do the job for the first time,
L= learning curve rate, between 0 and 1,
n = number of times the repeating time is doubled to reach x.
n and x
n  log2 x
If x  1, thenlog21  0;
If x  2, thenlog2 2  1;
If x  3, thenlog2 3  1.585;
If x  4, thenlog2 4  2;
If x  5, thenlog2 5  2.322;
If x  6, thenlog2 6  2.585;
If x  7, thenlog2 7  2.807;
If x  8, thenlog2 8  3;
If x  9, thenlog2 9  3.17;
Example
• The first time a task took a worker 12 hours to
complete. Suppose the learning curve rate is
85%. How long it would take that worker to
do the same task for the 16th time.
• The repeating time is doubled 4 times
(2,4,8,16) to reach 16. So,
T16 = 12 * 0.854 = 12*0.522 = 6.26 hrs
Ideas Contained in Learning Curve
• It would take less and less time for a
worker to do a job again and again.
• The performance time would decrease
by a certain rate after the number of
times repeated doubles.
Learning Curve Coefficient Table
• Table11-9, p.437, provides values learning
n
log x
curve coefficient, LCCx= L
= L , so that
Tx=T1* LCCx.
• The first column are values of x.
• Five learning curve rates, L’s, are in the table.
• For each rate L, “unit time” column gives
values of LCCx, “total time” column gives
cumulative LCC values LCC1+LCC2+LCC3+...
2
Example p.436
• Estimate the time to complete an order of 24
conveyor bucket systems. Suppose the first
system is estimated to need 120 hours, and
learning curve rate L=85%.
(1) Time to finish the 12th system?
(2) Time to finish the 24th system?
(3) Total hours needed for all the 24 systems?
Use of Learning Curve
• Learning curve is important in planning labor
and resource needed, scheduling, and
estimating cost for internal production or
negotiation with the contractor to do the
production.
Sensitivity of L on the Result
• The learning curve result is sensitive to value
of rate L, as below, assuming T1=1.
Total Production Cost
Production amount
Learning curve rate
85%
Learning curve rate
87%
% Cost Increase
1
1.0
1.0
0.0
10
5.8
6.3
8.6
100
34
39.6
16.4
1,000
198
249.6
26.1
10,000
1153.8
1571.6
36.2
100,000
6724.7
9895.5
47.2
How to Determine Rate L?
• From the historical records on the same or
similar job.
• Do experiments if possible.
• Subjective estimate based on experience.
• Since value of L affects the result of learning
curve calculation significantly, be cautious. A
pragmatic method is to give the range of rate
L, instead of a single value.