The new CEO of a store announced that average customer waiting times will be reduced by the extra sales staff she has employed.Previously, customers had to wait an average of 15 minutes to be served. After the extra staff began working, a random sample of 25 customers had an average waiting time of 10.98 minutes to be served with a standard deviation of 2.5 minutes.Assume the conditions for testing are satisfied.

The hypotheses to test the CEO's announcement, are as follows:

Ho: = 15

Ha: < 15

Give the calculated test statistic, critical value if testing at of 1%, your decision, explaining your reasoning and your conclusion.