Solve the problem.
-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 is less than 8.9 hours.
A) 0.4276
B) 0.9608
C) 0.9756
D) 0.9589

Question

Quizplus · Accepted Answer

The sampling distribution of the sample mean will be approximately normal with mean 8.4 and standard deviation 1.8/√40. Using the z-score formula, the z-score for 8.9 is calculated and then the corresponding probability is found using the standard normal distribution table.

Solve the Problem. -A Study of the Amount of Time It Takes a It