1. Chapter 25 Time Study Supplementary Material from:
Learning Objective 6
Determine the time required to do a job using standard data, occurrence sampling, time study, and predetermined time systems.
Supplementary Material from:
Groover, M.P. (2007). Work Systems and the Methods, Measurement, and Management of Work,
Upper Saddle River, NJ: Pearson Prentice Hall, pp

2. Time Study Also known as Involves Allowances made for
Direct Time Study
Stopwatch Time Study
Involves
direct, continuous observation of a task
using a time measurement instrument
to record time taken to complete task.
Allowances made for
personal needs
fatigue
unavoidable delays
Dates back to 1883
Inextricably connected with origins and early history of IE

3. Direct Time Study Procedure
Define and Document Standard Method
Divide Task Into Work Elements
Time Work Elements
Rate Worker’s Performance
Apply Allowances

4. Define and Document Standard Method
Goal: “one best method”
Seek worker’s advice, if appropriate
Elements of Document
Procedure (steps, actions, work elements, hand/body motions)
Tools, equipment
Machine settings (e.g., feeds, speeds)
Workplace layout
Frequency of irregular elements
Working conditions
Setup

5. Reasons For Thorough Documentation
Batch production (likely to be repeated)
Methods improvement by operator
Disputes about method (too tight?)
Data for standard data system

6. Divide Task Into Work Elements
Series of motion activities logically grouped because of unified purpose.
Guidelines
Each work element should consist of a logical group of motion elements.
e.g., reach, grasp, move, place
Beginning point of one element should be end of previous.
No time gap between elements.
Each element should have readily identifiable end point.
i.e., easily detected, no ambiguity
Work elements should not be too long.
< “several” min

7. Divide Task Into Work Elements
Guidelines (continued)
Work elements should not be too short.
> 3 sec
Irregular elements should be identified & distinguished.
i.e., not every cycle
Manual elements should be separated from machine elements.
generally constant values
Internal elements should be separated from external elements.
i.e., performed by operator during machine cycle

8. “Irregular” and “Foreign” Elements
Elements that occur routinely, but not every cycle – should be included: irregular elements (Groover)
Elements that the observer didn’t anticipate –probably should be included: irregular elements (Konz & Johnson)
Elements that are not normal work – should not be included: foreign elements (Konz & Johnson)

9. Time Work Elements
Collect data on time study form (on clipboard).

10. Time Work Elements (2)
Collect data on time study form (on clipboard).

11. Time Work Elements (3) Use stopwatch calibrated in 0.01 minutes:
Snapback method
Start watch at beginning of every element.
“Snap” watch back to zero at end of element.
Record time.
Advantages
Element variations easily observable
No subtraction
Continuous method
Start watch at beginning of observation (or beginning of each cycle)
Record elapsed time at end of each element.
Let it run …
Not so much manipulation of stopwatch
Elements not so easily omitted
Regular/irregular elements more readily distinguished (?)

12. Rate Worker’s Performance
Standard performance = 100%
Rate
Individual elements
Or entire work cycle
Most difficult & controversial step in time study
Requires analyst’s judgment

13. Apply Allowance Pure Manual Work
Work Element a b c d*
Obs. Time
0.56 min
0.25 min
0.50 min
1.10 min
Perf. Rating
100%
80%
110%
* irregular element performed every 5 cycles
PFD Allowance = 15%

14. Apply Allowance Pure Manual Work
Work Element a b c d*
Obs. Time
0.56 min
0.25 min
0.50 min
1.10 min
Perf. Rating
100%
80%
110%
* irregular element performed every 5 cycles
PFD Allowance = 15%
Normal Time:
NT = 0.56(1.00) (0.80) (1.10) (1.00)/5
= = 1.53 min
Standard Time:
ST = 1.53( ) = 1.76 min

15. Apply Allowance Task Including Machine Cycle
Work Element a b c d*
Obs. Time
0.22 min
0.65 min
0.47 min
0.75 min
Perf. Rating
100%
80%
Mach. Time
(idle) m
1.56 min
PFD Allowance = 15%
Machine Allowance = 20%
* irregular element performed every 15 cycles

16. Apply Allowance Task Including Machine Cycle
Work Element a b c d*
Obs. Time
0.22 min
0.65 min
0.47 min
0.75 min
Perf. Rating
100%
80%
Mach. Time
(idle) m
1.56 min
PFD Allowance = 15%
Machine Allowance = 20%
* irregular element performed every 15 cycles
Normal Time:
NT = 0.22(1.00) + Max{0.65(0.80), 1.56} (1.00) (1.00)/15
= = 2.30 min
Standard Time:
ST = ( )( )
+ Max{0.52( ), 1.56( )}
= = 2.72 min

17. Number of Cycles To Be Timed
Let X be a random variable, time of one work element in a task.
Time several cycles to estimate true mean:
close estimate
α/2
1-α x
α/2
1-α x
α/2
1-α x
low estimate
high estimate μX
Overall, P(μx lies within x + zα/2 [σ/√nc ]) = 1 – α
where nc = number of cycles timed
But σ unknown, so take preliminary sample of ns observations and use
∑(x-x)2
s =
ns-1

18. Number of Cycles To Be Timed (2)
P(μ lies within x + tα/2 [s/√nc ]) = 1 – α
Interval size = x + kx
where k = proportion of sample mean
(e.g., if k = 10%, interval size = x x)
kx = tα/2 [s/√nc ] (remember, s is an estimate of σ based on preliminary sample of ns)
So, rearranging,
nc = (tα/2s / kx)2

19. Number of Cycles To Be Timed: Example
From preliminary study, engineer has collected ns=10 samples on one work element
x = 0.40 min
s = 0.07 (an estimate of σ based on preliminary sample of ns=10)
How many cycles should be timed to ensure actual element time is + 10% of the sample mean, with 95% confidence?
df = (ns – 1) = 10 – 1 = 9
α = 0.05, α/2 = 0.025
tα/2 = t0.025 = 2.262
Number of cycles = nc = (tα/2s / kx)2 = [2.262(0.07) / 0.10(0.40)]2
= 15.7 ≈ 16 cycles
If 16 observed cycles yields
x = 0.45 min
P(μx lies within x + kx) = P(μx lies within (0.45))
= P(μx lies within [0.405, 0.495]) = 95%

20. Performance Rating Also called performance leveling.
Performance relative to engineer’s concept of “standard” performance.
Most common method based on speed or pace: speed rating.
> 100% means faster than standard pace
engineer must use judgment
must consider
degree of difficulty of work element
worker’s pace relative to standard
Standards
Walk 3 mi/hr on flat, level ground, no load, 27-in steps.
Problem: few work situations lend themselves to such precise measurement.
However, many situations in which experts judge (e.g., gymnastics, dog shows)
Solutions
Experience (including feedback)
Training (e.g., using training films)

21. Performance Rating (2) Pace depends on worker’s
skill
experience
exertion level
attitude toward time study
So, select skilled worker
familiar with job
Accepts time study as necessary management tool
Characteristics of good performance rating system
consistency among tasks (one task to another)
consistency among engineers
easily understood
related to standard performance (well-defined concept)
machine-paced elements rated at 100% (no worker control of machine)
rating recorded during observation, not after
worker notification

22. Time Study Issue Why is time study important to the organization?
What are some worker concerns?
How can they be resolved?

23. Time Study Equipment: Mechanical Stopwatch 1

24. Time Study Equipment: Mechanical Stopwatch 2

26. Time Study Results (from text)