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.

8

Specialized Non-Professional Jobs Management’s View

Advantages:• Readily available labor• Minimal training

required• Reasonable wages costs• High productivity

Disadvantages:• High absenteeism• High turnover rates• High scrap rates• Grievances filed

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Specialized Non-Professional JobsEmployee’s View

Advantages:• Minimal credentials

required• Minimal responsibilities• Minimal mental effort

needed• Reasonable wages

Disadvantages:• Boredom• Little growth opportunity• Little control over work• Little room for initiative• Little intrinsic satisfaction

Eliminating Employee BoredomEnhance 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 and standard deviation s.

• Calculate minimum observations, n:

where

z= number of standard deviations for desired confidence, see Table 11-3 on p.425;

a = desired accuracy as % of mean time , 5% for example.x

X

2

X

s

a

zn

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:

Note: Discussions of AF in the textbook on p.427 are confusing. Ignore the concept of AFjob.

PFDAF

1

1

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 and standard deviation s. x

Steps for Setting Standard Times of an Element by Time Study (2)

• Determine number of observations required, n:

where z= number of standard deviations for desired confidence, see

Table 11-3 on p.425;a = desired accuracy as % of mean time , 5% for example.

2

X

s

a

zn

x

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”:

Note: Ignore the formula AF=1+PFDgiven in book.

• Calculate “standard time ST” of the element:ST = (NT)(AF).

PFDAF

1

1

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:

where

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.

)1(2

ppe

zn

Steps of Doing Work Sampling

• Run 30 trial observations. p = (number of times doing the activity) / 30.

• Calculate number of observations:

• Run (n-30) more observations.• Calculate p based on n observations

p = (number of times doing the activity) / n.

)1(2

ppe

zn

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• Tx = T1 * Ln = T1 * Llog

2x

• 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

xn 2log0; 1log then 1, xIf 2 1; 2log then 2, xIf 2

1.585; 3log then 3, xIf 2 2; 4log then 4, xIf 2

2.322; 5log then 5, xIf 2 2.585; 6log then 6, xIf 2

2.807; 7log then 7, xIf 2 3; 8log then 8, xIf 2 3.17; 9log then 9, xIf 2

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 curve coefficient, LCCx= Llog

2x = Ln, 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+...

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.

Production amount

Total Production Cost

% Cost Increase Learning curve rate

85% Learning curve rate

87%

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.