A time-study analyst is determining the standard time for a work element.The select time is 6.0 minutes,and the standard deviation of the select time is 2.2 minutes,based on a pilot sample of 20 observations.What is the appropriate sample size if the estimate for the select time is to be within 10 percent of the true average time 95 percent of the time?
A) Fewer than 30 observations
B) Greater than or equal to 30 observations but fewer than 40 observations
C) Greater than or equal to 40 observations but fewer than or equal to 50 observations
D) Greater than or equal to 50 observations

Question

Quizplus · Accepted Answer

To find the appropriate sample size, we need to use the formula:
n = [(z * σ) / E]^2
where z is the confidence level (1.96 for 95% confidence level), σ is the standard deviation (2.2 minutes), and E is the desired margin of error (10% of the true average time, which is 0.1 * 6.0 = 0.6 minutes). Therefore, we have:
n = [(1.96 * 2.2) / 0.6]^2 = 49.95, which rounds up to 50.
Thus, the appropriate sample size is greater than or equal to 50 observations, so the answer is D.

A Time-Study Analyst Is Determining the Standard Time for a Work