1. ME 5211, IE 5511, HUMF 5211:
Human Factors and Work Analysis
Final Exam Review Practice Questions
Solutions adapted from NIEBEL’S
METHODS, STANDARDS
AND WORK DESIGN
Chapter 11
Questions: 13, 17, 18; Problems: 2, 3, 8
13. Would there be any objection to studying an operator who was performing at an excessive pace?
Why
or why not?
It is preferable to study an operator who is working at a more standard pace. It is difficult to evaluate
accurately performances at either end of the rating scale. Novice analysts tend to rate above- standard
performance too low and below-standard performance too high (regression toward the mean.)
17. What are some of the major factors that affect fatigue?
Illumination, noise, temperature, humidity, ventilation, weight of loads, posture, monotony of the
task, repetitiveness of the task, mental strain of the task, etc. all affect fatigue.
18. Which operator interruptions would be covered by the unavoidable delays allowance?
Unavoidable delays cove interruptions from the supervisor, dispatcher, time study analyst, material
irregularities, interference delays, etc.
2. Develop an allowance factor for an assembly element where the operator is standing in a slightly
awkward position, regularly lifts a weight of 15 pounds, and has good light and atmospheric
conditions. The attention required is fine, the noise level is continuous at 70 dBA, and the mental
strain is low, as is the monotony and the tediousness of the work.
Constant allowance = 9%
Standing = 2%
Weight lifted (15 lbs) = 2%
Fine attention = 2%
Total = 15%
3. Calculate the fatigue allowance for an operation for which the operator loads and unloads a
25-pound gray iron casting once every five minutes at a height of 30 inches.
Using the NIOSH lifting guidelines (assume H=10 inches, 8-hour shift, good coupling, and no
twisting):
RWL (lbs) = 51 × (10/H) × (1 - 0.0075|V-30|) × (0.82 + 1.8/D) × (1 - 0.0032×A) × FM × CM
RWL (lbs) = 51 × (10/10) × (1 - 0.0075|30-30|) × (0.82 + 1.8/0) × (1 - 0.0032×0) × 0.85 × 1
RWL (lbs) = 51 × 1 × 1 × 1 × 1 × 0.85 × 1 = 43.35 and
LI = 25/43.35 = 0.58 which is acceptable and no allowance is needed
8. Calculate the fatigue allowance for a worker shoveling scrap metal into a bin. His working heart rate
is approximately 130 beats/min.
RA = (ΔH/40 -1) × 100 = [(130-72)/40 - 1] × 100 = 45%

2. Chapter 14
Questions: 2, 4, 8; Problems: 3, 4, 6
2. What are advantages of work sampling over stopwatch time study?
Continuous observations not required less clerical time fewer analyst hours expended operator not
subjected to long observation periods crew operations easily studied by one analyst
4. How is it possible to determine the time of day to make the various observations so that biased results
do not occur?
Use a table of random numbers and convert the random number into specific times of the day. For
example use the first two digits for hours of the day (military time) and next two digits for minutes of the
hour. A simpler approach is to use a random number generator on a PC or a PDA or in DesignTools.
8. Over how long a period is it desirable to collect observations?
One should sample until a cumulative plot of the information being sought levels off.
3. The superintendent estimated the downtime to be about 30 percent.
The desired results, using a work sampling study, are to be within ±5 percent of p with a level of
significance of 0.95. The analyst decides to take 300 random readings a day for three weeks. Develop
a p chart for p = 0.30 and subsample size N = 300. Explain the use of this p chart.
R = 3σ = 3[p(1-p)/n].5 = 3[0.3 × 0.7 / 300].5 = 0.0794
Set up control limits of 0.30 ± 0.08. Each day take readings and plot p. If daily readings are within
the ± 0.08 tolerance, then continue with a daily sample size of 300 for the rest of the three-week
study. Then compute the final estimate value of p from the data.
4. The Dorben Company is using the work sampling technique to establish standards in its typing pool
section. This pool has varied responsibilities, including typing from tape recordings, filing, Kardex
posting, and copying. The pool has six typists who work a 40-hour week. Seventeen hundred random
observations were made over a four-week period. During the period, the typists produced 9,001
pages of routine typing. Of the random observations, 1,225 showed that typing was taking place.
Assuming a 20 percent allowance and an adjusted performance rating factor of 0.85, calculate the
hourly standard per page of typing.
OT = T × ni = (4×6×40) × 1,225 = 0.0769 hrs/page
P × n 9,001 × 1,700
NT = OT × R/100 = 0.0769 × 0.85 = 0.06537
ST = NT × (1 + Allow) = 0.06537 × (1 + 0.20) = 0.07844 hrs/page
This can also be represented as 12.8 pages/hour.
6. To get ±5 percent precision on work that is estimated to take 80 percent of the workers' time, how
many random observations are required at the 95 percent confidence level?
n = 3.84p(1-p)/R2 where R = 0.05 × 0.80 = 0.04
n = 3.84 × 0.80 × (1 - 0.80) / 0.042 = 384 observations