The owner of two submarine sandwich shops located in Gainesville, Florida, would like to know how the mean daily sales of the first shop (located in the downtown area) compares to that of the second shop (located on the southwest side of town). In particular, he would like to know whether the mean daily sales levels of these two restaurants are essentially equal. He records the sales (in dollars) made at each location for 30 randomly chosen days. These sales levels are given in the file P10_19.XLS. Construct a 99% confidence level for the mean difference between the daily sales of restaurant 1 and restaurant 2. Use this confidence interval to answer the following questions:

a. Is it possible to conclude that a statistically significant mean difference exists at the 1% level of significance? Explain why or why not.

b. Is it possible to conclude that a statistically significant mean difference exists at the 5% level of significance? Explain why or why not.

c. Is it possible to conclude that a statistically significant mean difference exists at the 10% level of significance? Explain why or why not.