Question

A national study of people who purchase cars found the mean age of a car buyer to be 48 and the population standard deviation 4 years. Your dealership decides to see if your customers fit this same pattern. A sample of 80 customers found the mean to be 46 years of age. Are your customers younger than the national average at the .005 level of significance? Use the five-step procedure to answer the question and include the p-value.

Answer 1

Solution :

This is the two tailed test .

The null and alternative hypothesis is ,

H₀ :   = 48

H_a :    48

Test statistic = z

= ( - ) / / n

= (46 - 48) / 4 / 80

= -4.47

P(z < -4.47) = 0

P-value = 2 * 0 = 0

= 0.005

P-value <

Reject the null hypothesis .