Suppose it is desired to estimate the average time a customer spends in a particular store to within 5 minutes (e.g., + 5 minutes) at 97% reliability. It is estimated that the standard deviation of the times is 15 minutes. How large a sample should be taken to get the desired interval?
A) n = 6.51
B) n = 150
C) n = 43
D) n = 7

Question

Quizplus · Accepted Answer

To find the sample size, use the formula n = (Z*σ/E)^2, where Z is the z-score for 97% confidence (approximately 2.17), σ is the standard deviation (15 minutes), and E is the margin of error (5 minutes). Calculating gives n ≈ 43.

Suppose It Is Desired to Estimate the Average Time a Customer