A study of the amount of time it takes a mechanic to rebuild the transmission for a 2005 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard deviation is 1.8 hours. If 40 mechanics are randomly selected, find the probability that their mean rebuild time exceeds 8.1 hours.
A) 0.8531
B) 0.9146
C) 0.8457
D) 0.7285

Question

Quizplus · Accepted Answer

The probability that the mean rebuild time exceeds 8.1 hours is 0.8531. This is because the z-score for a mean rebuild time of 8.1 hours is (8.1 - 8.4) / 1.8 = -0.17. The probability that a z-score is less than -0.17 is 0.8531.

A Study of the Amount of Time It Takes a Mechanic