1. Work Study
Work Measurement

2. Outline Labor Standards and Work Measurement Historical Experience
Time Studies
Predetermined Time Standards
Work Sampling 2

3. 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
This slide provides some reasons that capacity is an issue. The following slides guide a discussion of capacity. 3

4. Meaningful Standards Help Determine
Labor content of items produced
Staffing needs
Cost and time estimates
Crew size and work balance
Expected production
Basis of wage incentive plans
Efficiency of employees
This slide can be used to frame a discussion of capacity.
Points to be made might include:
- capacity definition and measurement is necessary if we are to develop a production schedule
- while a process may have “maximum” capacity, many factors prevent us from achieving that capacity on a continuous basis.
Students should be asked to suggest factors which might prevent one from achieving maximum capacity. 4

5. Labor Standards May be set in four ways: Historical experience
Time studies
Predetermined time standards
Work sampling

6. 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

7. 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

8. Time Studies Define the task to be studied
Divide the task into precise elements
Decide how many times to measure the task
Time and record element times and rating of performance

9. Time Studies Compute average observed time
Sum of the times recorded to perform each element
Number of observations =
Determine performance rating and normal time
Normal time = x
Average observed time
Performance rating factor

10. Time Studies
Add the normal times for each element to develop the total normal time for the task
Compute the standard time
Standard time =
Total normal time
1 - Allowance factor

11. Rest Allowances Personal time allowance Delay 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

12. 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
Very awkward (lying, stretching) …………………… 7
Figure S10.1

13. Rest Allowances
Use of force or muscular energy in lifting, pulling, pushing
Weight lifted (pounds)
20 …………………………………… 3
40……………………………………. 9
60……………………………………. 17
Bad light:
Well below recommended…. 2
Quite inadequate……………. 5
Figure S10.1

14. Rest Allowances
(E) Atmospheric conditions (heat and humidity) …………… 0-10
Close attention:
(i) Fine or exacting……………….. 2
(ii) Very fine or very exacting…… 5
Noise level:
(i) Intermittent—loud…………….. 2
(ii) Intermittent—very loud or high-pitched………………... 5
Figure S10.1

15. Rest Allowances Mental strain:
(i) Complex or wide span of attention.…………………….. 4
(ii) Very complex………………….. 8
Tediousness:
(i) Tedious…………..……………… 2
(ii) Very tedious.…………………… 5
Figure S10.1

16. 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
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before.
Standard time = = =
Normal time
1 - Allowance factor
3.4
.87
= 3.9 minutes 16

17. Time Study Example S2 Allowance factor = 15%
Performance
Job Element Rating
Compose and type letter * %
Type envelope address %
Stuff, stamp, seal, and 2 1 5* % sort envelopes
Cycle Observed (in minutes)
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before.
Delete unusual or nonrecurring observations (marked with *)
Compute average times for each element
Average time for A = ( )/4 = 9.5 minutes
Average time for B = ( )/5 = 2.2 minutes
Average time for C = ( )/4 = 1.5 minutes 17

18. Time Study Example S2 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
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before.
Add the normal times to find the total normal time
Total normal time = = minutes 18

19. Time Study Example S2 15.36 = = 18.07 minutes 1 - .15
Compute the standard time for the job
Standard time =
Total normal time
1 - Allowance factor
= = minutes
15.36
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before. 19

20. Determine Sample Size How accurate we want to be
The desired level of confidence
How much variation exists within the job elements
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before. 20

21. Determine Sample Size zs hx Required sample size = n =2 zs 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
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before. 21

22. Determine Sample Size zs hx Required sample size = n = Common z Values2 zs hx
Common z Values
Desired Confidence (%)
z Value
(standard deviation required for desired level of confidence)
90.0
1.65
95.0
1.96
95.45
2.00
99.0
2.58
99.73
3.00
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
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before.
Table S10.1 22

23. 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)
n = 2 zs hx
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before.
n = = ≈ 171 2
1.96 x 1.0
.05 x 3 23

24. Time Study Example S3 Variations
If desired accuracy h is expressed as an absolute amount, substitute e for hx, where e is the absolute amount of acceptable error
n = 2 zs e
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before.
When the standard deviation s is not provided, it must be computed
s = =
∑(xi - x)2 ∑(Each sample observation - x)2
n - 1 Number in sample - 1 24

25. New Tools
With PDA software, you can study elements, time, performance rate, and statistical confidence intervals can be created, edited, managed, and logged
Reduces or eliminates the need for data entry
It might be useful at this point to discuss typical equipment utilization rates for different process strategies if you have not done so before. 25

26. 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
You might point out to students that this slide links capacity to work measurement (standard times). 26

27. MTM Table
Figure S10.2

28. .0006 x 238 = Total standard minutes = .14
MTM Example
Weight - less than 2 pounds
Conditions of GET - easy
Place accuracy - approximate
Distance range - 8 to 20 inches
Element Description
Element
Time
Get tube from rack
AA2 35
Get stopper, place on counter
Get centrifuge tube, place at sample table
AD2 45
Pour (3 seconds) PT 83
Place tubes in rack (simo)
PC2 40
Total TMU
238
.0006 x 238 = Total standard minutes = .14
Table S10.2

29. 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

30. 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

31. 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

32. Work Sampling
Take a preliminary sample to obtain estimates of parameter values
Compute the sample size required
Prepare a schedule for random observations at appropriate times
Observe and record worker activities
Determine how workers spend their time

33. Work Sampling Determining the sample size z2 p(1 - p) h2 n =
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

34. 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
n =
z2 p(1 - p) 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
n = = 833 observations
(2)2 (.25)(.75)
(.03)2

35. Work Sampling Example All but idle and personal time are work related.
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 = ( )/833 = 22.6%.
Since this is less than the target value of 25%, the workload needs to be adjusted.

36. Work Sampling Time Studies
Salespeople
Sales in person
20%
Travel
20%
Telephone sales
12%
Paperwork
17%
Lunch and personal
10%
Telephone within firm
13%
Meetings and other 8%
Figure S10.3 36

37. Work Sampling Time Studies
Startup/pep talk 3%
Assembly-Line Employees
Breaks and lunch
10%
Dead time between tasks
13%
Productive work
67%
Unscheduled tasks and downtime 4%
Cleanup 3%
Figure S10.3 37