The mean waiting time at the drive-through window at a local McDonald's is 85.6 seconds. The manager devises a new drive-through system that she believes will decrease wait time. Using the new system, a random sample of 25 customer's times at the drive-through window is obtained with a sample mean of 84.5 seconds and a standard deviation of 3.4 seconds. Test the claim that the new system lowers the wait time using a=0.05

a) What sampling distribution applies in this case? Will you need to use the t-distribution or the normal?


b) What assumptions about the sample and the population need to be made? And what types of tests are necessary to demonstrate that the conditions are met?