Question

The owner of a local chain of grocery stores is always trying to minimize the time it takes her customers to check out. In the past, she has conducted many studies of the checkout times, and they have displayed a normal distribution with a mean time of 12.8 minutes. and a standard deviation of 3 minutes. She has implemented a new schedule for cashiers in hopes of reducing the mean checkout time. A random sample of 25 customers visiting her store this week resulted in a mean of 11.9 minutes. Does she have sufficient evidence to claim the mean checkout time this week was less than 12.8 minutes? Use α = .02.

(a) Find z. (Give your answer correct to two decimal places.)

(ii) Find the p-value. (Give your answer correct to four decimal places.)

(b) State the appropriate conclusion.

-Reject the null hypothesis, there is not significant evidence that the mean checkout time is less than 12.8 minutes.

-Reject the null hypothesis, there is significant evidence that the mean checkout time is less than 12.8 minutes.    

-Fail to reject the null hypothesis, there is significant evidence that the mean checkout time is less than 12.8 minutes.

-Fail to reject the null hypothesis, there is not significant evidence that the mean checkout time is less than 12.8 minutes.

Answer 1