Exhibit 9-4
The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took the customers in the sample to check out was 3.1 minutes with a standard deviation of 0.5 minutes. We want to test to determine whether or not the mean waiting time of all customers is significantly more than 3 minutes.
-Refer to Exhibit 9-4. At 95% confidence, it can be concluded that the mean of the population is
A)significantly greater than 3
B)not significantly greater than 3
C)significantly less than 3
D)significantly greater then 3.18

Question

Quizplus · Accepted Answer

We need to conduct a one-tailed t-test with a population mean of 3 and a sample size of 100, sample mean of 3.1, and a standard deviation of 0.5. Using a t-distribution table with 99 degrees of freedom and a 95% confidence level, the critical value is 1.660. The calculated t-value is (3.1-3)/(0.5/√100) = 2. This calculated t-value is greater than the critical value of 1.660, therefore we reject the null hypothesis and conclude that the mean of the population is significantly greater than 3 at a 95% confidence level.

Exhibit 9-4 The Manager of a Grocery Store Has Taken a Random