Question

In order to fairly set flat rates for auto mechanics, a shop foreman needs to estimate the average time it takes to replace a fuel pump in a car. How large a sample must he select if he wants to be 90% confident that the average time is within 20 minutes of the sample average? Assume the standard deviation of all times is 40 minutes.

Answer 1

ME = 1.96(45)/sqrt(n) 25 = 1.96(45)/sqrt(n) n = (1.96(45)/25)^2 = 6

Explanation:

yw