Chapter 07 – Work Design and Measurement
122. How many observations should be made if he wants to be 95.44 percent confident that
the maximum error in the observed time is one second?
The owner of Touchdown Sports Bar wants to develop a time standard for the task of mixing
a specialty cocktail. In a preliminary study, he observed one of his bartenders perform this
task seven times with an average of 90 seconds and a standard deviation of 5 seconds.
123. What is the normal time (NT) for this task if the bartender worked at a twenty percent
faster pace than is average?
Chapter 07 – Work Design and Measurement
124. What is the standard time (ST) for this task if the bartender worked at a twenty percent
faster pace than is average, and an allowance of twenty percent of the workday is used?
125. What is the standard time (ST) for this task if the bartender worked at a twenty percent
faster pace than is average, and an allowance of ten percent of job time is used?
Chapter 07 – Work Design and Measurement
126. How many observations should be made if he wants to be 95.44 percent confident that
the maximum error in the observed time is one second?
A Methods and Measurements Analyst for Digital Devices needs to develop a time standard
for the task of assembling a computer mouse. In a preliminary study, she observed one of her
workers perform this task six times with the following results:
127. What is the observed time (OT) for this task?
Chapter 07 – Work Design and Measurement
128. What is the normal time (NT) for this task if the employee worked at a 20% faster pace
than is average?
129. What is the standard time (ST) for this task if the employee worked at a 20% faster pace
than is average and an allowance of 25% of the workday is used?
Chapter 07 – Work Design and Measurement
130. What is the standard time (ST) for this task if the employee worked at a 20% faster pace
than is average and an allowance of 25% of job time is used?
131. How many observations should be made if she wants to be 0.8664 confident that the
maximum error in the observed time is 0.5 second? Assume that the standard deviation of the
task time is 4 seconds.
Chapter 07 – Work Design and Measurement
The manager of Lawn and Garden Services would like to estimate the proportion of her
employees’ time spent performing various gardening or lawn care activities. She has made
400 random observations of a typical worker, with the following results:
132. What is the most likely true proportion of time spent mowing?
133. What is the probability that the true proportion of time spent mowing is exactly equal to
the sample proportion?
Chapter 07 – Work Design and Measurement
134. How confident can the manager be that the true proportion of time spent mowing is
between .45 and .55?
135. Between what limits can the manager be 68.26 percent confident the true proportion of
time spent mowing is?
Chapter 07 – Work Design and Measurement
136. If the manager wants to be 95.44 percent confident that the true proportion of time spent
mowing is within .02 (plus or minus) of the sample proportion, what should be her sample
size?
137. What is the observed time for this task?
Chapter 07 – Work Design and Measurement
138. If the person observed worked at a pace that is 80 percent of normal, what should be the
normal time for this task?
139. If the person observed worked at a pace that is 80 percent of normal, and if the
appropriate allowance for this task is 25 percent of job time, what should be the standard
time?
140. If the person observed worked at a pace that is 20 percent faster than average, what
should be the normal time for this task?
Chapter 07 – Work Design and Measurement
141. If the person observed worked at a pace that is 20 percent faster than average, and if the
appropriate allowance for this task is 25 percent of the workday, what should be the standard
time?
142. How many observations would be needed to be 95.44% confident that the maximum
error in the observed time is 1 second? Assume that the standard deviation of the task time is
2 seconds.
143. How many observations would be needed to be 99.74% confident that the maximum
error is 5% of the observed time? Assume that the standard deviation of the task time is 2
seconds.
Chapter 07 – Work Design and Measurement
Given the following work sampling data, based upon 100 random observations of a particular
worker:
144. What is the estimated proportion of time this worker spends performing activity A?
145. For a confidence level of 86.64%, what is the maximum error of the estimate for activity
A?
Chapter 07 – Work Design and Measurement
146. For a confidence level of 95.44% and a maximum error of .04, what should be the
sample size for estimating the proportion of time spent performing activity A?
147. What is the estimated proportion of time this worker spends performing activity B?
148. What is the estimated proportion of time this worker spends on activities B and C?
Chapter 07 – Work Design and Measurement
149. For a confidence level of 95.44% and a maximum error of .04, what should be the
sample size for estimating the proportion of time spent performing activity B?
150. For a confidence level of 95.44% and a maximum error of .04, what should be the
sample size for estimating the proportion of time spent performing activity C?
151. For a confidence level of 86.64%, what is the maximum error of the estimate for activity
B?