An industrial engineer is conducting a time study for a work element. The select time is 4.5 minutes, and the sample standard deviation of the observed time is 20 seconds. What is the appropriate sample size if the estimate is to be 5 percent of the True average time 95 percent of the time?
A) fewer than or equal to seven
B) greater than seven but fewer than or equal to eight
C) greater than eight but fewer than or equal to nine
D) greater than nine

Question

Quizplus · Accepted Answer

To find the appropriate sample size, we need to use the formula: 
n = (Zα/2 * σ/ME)², where
Zα/2 = 1.96 (for a confidence level of 95%)
σ = sample standard deviation = 20 seconds
ME = margin of error = 0.05(True average time)

Plugging in the values, we get:
n = (1.96*20/0.05)²
n = 1536.64
Round it up to the nearest whole number: n = 1537

Therefore, the appropriate sample size is greater than eight but fewer than or equal to nine, which is option C.

An Industrial Engineer Is Conducting a Time Study for a Work