Statistics word problem

Question

A battery pack manufacturer claims their product will run two cell phones playing Pokemon go an average of 12 hours with a standard deviation of 2.4 hours. A random sample of 40 battery packs is tested. What is the probability the sample mean is above 13 hours?

Answer 1

You will need the z-score formula and the z-score table.

 

z = (13 - 12) / (2.4/√40) = 1/0.3795 = 2.64

 

Use the complement rule to find the probability that the sample mean is above 13 hours.

 

P(Z>2.64) = 1 - P(Z≤2.64) = 1 - 0.9959 = 0.0041

 

The probability that the sample mean is above 13 hours is 0.0041.