Exhibit 9-2
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. The population standard deviation is known to be 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 9-2. At a .05 level of significance, 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 can use a one-sample t-test since the population standard deviation is known and our sample size is greater than 30. Our null hypothesis is that the mean waiting time of all customers is 3 minutes (or less) and our alternative hypothesis is that the mean waiting time is more than 3 minutes. Using a t-test calculator, we find that the t-value is 3.46 and the p-value is less than .001. Since the p-value is less than .05, we reject the null hypothesis and conclude that the mean of the population is significantly greater than 3.

Exhibit 9-2 The Manager of a Grocery Store Has Taken a Random