PRODUCTION AND OPERATION

MANAGEMENT

WORK
MEASUREMENT

SESSION-17
LABOR STANDARDS AND WORK
MEASUREMENT

 Started early in the 20th century

 Important to both manufacturing and
service organizations
 Necessary for determining staffing
requirements
 Important to labor incentive systems

12-2
WORK MEASUREMENT
Vital inputs for:
• Manpower planning
• Reducing labour costs
• Scheduling
• Budgeting
• Designing incentive systems

Standard Time
Amount of time a qualified worker should spend to complete a
specified task, working at sustainable rate, using given methods,
tools and equipment, raw material and workplace
MEANINGFUL STANDARDS HELP
DETERMINE
1. Labor content of items produced
2. Staffing needs
3. Cost and time estimates
4. Crew size and work balance
5. Expected production
6. Basis of wage incentive plans
7. Efficiency of employees
MOST COMMONLY USED METHODS
OF WORK MEASUREMENT:
May be set in four ways:

1. Historical experience
2. Time studies
3. Predetermined time standards
4. Work sampling
HISTORICAL EXPERIENCE
 How the task was performed last
time
 Easy and inexpensive
 Data available from production
records or time cards
 Data is not objective and may be
inaccurate
 Not recommended
TIME STUDIES

 Involves timing a sample of a worker’s

performance and using it to set a
standard
 Requires trained and experienced
observers
 Cannot be set before the work is
performed
TIME STUDIES
1. Define the task to be studied
2. Divide the task into precise elements
3. Decide how many times to measure
the task
4. Time and record element times and
rating of performance
TIME STUDIES
5. Compute average observed time
Sum of the times recorded to perform
Average each element
observed time = Number of observations

6. Determine performance rating and

normal time
Average observed
Normal time = time x Performance rating
factor
TIME STUDIES
7. Add the normal times for each element
to develop the total normal time for the
task
8. Compute the standard time

Total normal time

Standard time = 1 - Allowance factor
REST ALLOWANCES
 Personal time allowance
 4% - 7% of total time for use of restroom,
water fountain, etc.
 Delay allowance
 Based upon actual delays that occur
 Fatigue allowance
 Based on our knowledge of human
energy expenditure
 REST ALLOWANCES
1. Constant allowance
(A) Personal allowance ……………... 5
(B) Basic fatigue allowance ………… 4
2. Variable allowances:
(A) Standing allowance ……………… 2
(B) Abnormal position
(i) Awkward (bending) ………… 2
(ii) Very awkward (lying,
stretching) …………………… 7
Figure S10.1
 REST ALLOWANCES
(C) Use of force or muscular energy in
lifting, pulling, pushing
Weight lifted (pounds)
20 …………………………………… 3
40……………………………………. 9
60……………………………………. 17
(D) Bad light:
(i) Well below recommended…. 2
(ii) Quite inadequate……………. 5
Figure S10.1
 REST ALLOWANCES
(E) Atmospheric conditions
(heat and humidity) …………… 0-10
(F) Close attention:
(i) Fine or exacting……………….. 2
(ii) Very fine or very exacting…… 5
(G) Noise level:
(i) Intermittent—loud…………….. 2
(ii) Intermittent—very loud
or high-pitched………………... 5
Figure S10.1
 REST ALLOWANCES
(H) Mental strain:
(i) Complex or wide span
of attention.…………………….. 4
(ii) Very complex………………….. 8
(I) Tediousness:
(i) Tedious…………..……………… 2
(ii) Very tedious.…………………… 5

Figure S10.1
TIME STUDY EXAMPLE S1
Average observed time = 4.0 minutes
Worker rating = 85%
Allowance factor = 13%

Normal time = (Average observed time) x (Rating factor)

= (4.0)(.85)
= 3.4 minutes

Normal time 3.4 3.4

Standard time = = = .87
1 - Allowance factor 1 - .13

= 3.9 minutes
 TIME STUDY EXAMPLE S2
Allowance factor = 15%

Cycle Observed (in minutes)

Performance
Job Element 1 2 3 4 5 Rating
(A) Compose and type letter 8 10 9 21* 11 120%
(B) Type envelope address 2 3 2 1 3 105%
(C) Stuff, stamp, seal, and 2 1 5* 2 1 110%
sort envelopes

1. Delete unusual or nonrecurring observations (marked with *)

2. Compute average times for each element
Average time for A = (8 + 10 + 9 + 11)/4 = 9.5 minutes
Average time for B = (2 + 3 + 2 + 1 + 3)/5 = 2.2 minutes
Average time for C = (2 + 1 + 2 + 1)/4 = 1.5 minutes
TIME STUDY EXAMPLE S2
3. Compute the normal time for each element

Normal time = (Average observed time) x (Rating)

Normal time for A = (9.5)(1.2) = 11.4 minutes

Normal time for B = (2.2)(1.05) = 2.31 minutes
Normal time for C = (1.5)(1.10) = 1.65 minutes

4. Add the normal times to find the total normal time

Total normal time = 11.40 + 2.31 + 1.65 = 15.36 minutes

TIME STUDY EXAMPLE S2
5. Compute the standard time for the job

Total normal time

Standard time =
1 - Allowance factor

15.36
= 1 - .15 = 18.07 minutes
DETERMINE SAMPLE SIZE

 How accurate we want to be

 The desired level of confidence
 How much variation exists within the
job elements
DETERMINE SAMPLE SIZE
2
zs
Required sample size = n =
hx

where h = accuracy level desired in percent of the job element

expressed as a decimal
z = number of standard deviations required for the desired
level of confidence
s = standard deviation of the initial sample
x = mean of the initial sample
n = required sample size
DETERMINE SAMPLE SIZE
2
Common z Values zs
Required sample size = n =
hx
Desired z Value
Confidence (standard deviation required for
(%) desired level of confidence)
where h = accuracy level desired in percent of the job element
90.0
expressed as a decimal 1.65
z =95.0
number of standard deviations 1.96required for the desired
level of confidence
s =95.45 2.00
standard deviation of the initial sample
x =99.0
mean of the initial sample 2.58
n =99.73
required sample size 3.00

Table S10.1
TIME STUDY EXAMPLE S3
Desired accuracy with 5%
Confidence level = 95%
Sample standard deviation = 1.0
Sample mean = 3.00

h = .05 x = 3.00 s = 1.0

z = 1.96 (from Table S10.1 or Appendix I)

zs 2
n= hx

2
1.96 x 1.0
n= .05 x 3 = 170.74 ≈ 171
PREDETERMINED TIME STANDARDS
 Divide manual work into small basic
elements that have established times
 Can be done in a laboratory away from the
actual production operation
 Can be set before
the work is actually
performed
 No performance
ratings are necessary
MTM
 Methods-Time Measurement (MTM) is a
predetermined motion time system that is
used primarily in industrial settings to
analyze the methods used to perform any
manual operation or task and, as a product
of that analysis, set the standard time in
which a worker should complete that task.

12-25
WORK SAMPLING
 Estimates percent of time a worker
spends on various tasks
 Requires random observations to
record worker activity
 Determines how employees allocate
their time
 Can be used to set staffing levels,
reassign duties, estimate costs, and set
delay allowances
WORK SAMPLING
 Advantages of work sampling
 Less expensive than time study
 Observers need little training
 Studies can be delayed or interrupted
with little impact on results
 Worker has little
chance to affect
results
 Less intrusive
WORK SAMPLING
 Disadvantages of work sampling
 Does not divide work elements as
completely as time study
 Can yield biased results if observer does
not follow random pattern
 Less accurate, especially when
job element times are short
WORK SAMPLING
1. Take a preliminary sample to obtain
estimates of parameter values
2. Compute the sample size required
3. Prepare a schedule for random
observations at appropriate times
4. Observe and record worker activities
5. Determine how workers spend their
time
WORK SAMPLING
Determining the sample size
z2 p(1 - p)
n=
h2
where n = required sample size
z = standard normal deviate for desired confidence
level
p = estimated value of sample proportion
h = acceptable error level in percent
WORK SAMPLING EXAMPLE
Wants employees idle 25% of the time
Sample should be accurate within 3%
Wants to have 95.45% confidence in the results

z2 p(1 - p)
n= h2

where n = required sample size

z = 2 for a 95.45% confidence level
p = estimate of idle proportion = 25% = .25
h = acceptable error of 3% = .03

(2)2 (.25)(.75)
n= (.03)2 = 833 observations
WORK SAMPLING EXAMPLE
No. of
Observations Activity
485 On the phone or meeting with a welfare client
126 Idle
62 Personal time
23 Discussions with supervisor
137 Filing, meeting, and computer data entry
833
All but idle and personal time are work related.
Percentage idle time = (126 + 62)/833 = 22.6%.
Since this is less than the target value of 25%, the workload needs to
be adjusted.
 WORK SAMPLING TIME STUDIES
Salespeople

Sales in Travel
person 20%
20%
Telephone
sales Paperwork
12% 17%
Lunch and
personal
10%
Telephone
within firm Meetings
13% and other
Figure S10.3
8%
 WORK SAMPLING TIME STUDIES
Startup/pep talk
Assembly-Line 3%
Employees
Breaks and lunch
10%

Dead time
between tasks
13%
Productive Unscheduled tasks
work and downtime
67% 4%
Cleanup
3%

Figure S10.3