# How many observations should a time study analyst plan for in an operation that has a standard deviation of 1.5 minutes per piece if the goal is to estimate the mean time per piece to within .4 minute with a confidence of 95.5 percent?

How many observations should a time study analyst plan for in an operation that has a standard
deviation of 1.5 minutes per piece if the goal is to estimate the mean time per piece to within
.4 minute with a confidence of 95.5 percent?

. How many work cycles should be timed to estimate the average cycle time to within 2 percent of
the sample mean with a confidence of 99 percent if a pilot study yielded these times (minutes):
5.2, 5.5, 5.8, 5.3, 5.5, and 5.1? The standard deviation is .253 minutes per cycle.

. In an initial survey designed to estimate the percentage of time air-express cargo loaders are idle,
an analyst found that loaders were idle in 6 of the 50 observations.
a. What is the estimated percentage of idle time?
b. Based on the initial results, approximately how many observations would you require to estimate the actual percentage of idle time to within 5 percent with a confidence of 95 percent?