A store manager claims that the average age of his customers is less than 40 years old, while the industry average is 40 years old. He asks you to test his thinking. You collect a sample of 50 customers and found that the average age is 38.7. Assuming that the population standard deviation is 12.5 years and using α = 0.05, test your manager's hypothesis. What is your conclusion?

Question

A store manager claims that the average age of his customers is less than 40 years old, while the industry average is 40 years old. He asks you to test his thinking. You collect a sample of 50 customers and found that the average age is 38.7. Assuming that the population standard deviation is 12.5 years and using α = 0.05, test your manager's hypothesis. What is your conclusion?

Answer 1

Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√n

If only one SD is provided, you can use just that to determine SEdiff.

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.