A stock analyst wants to determine whether there is a difference in the mean rate of return for three types of stock: utility, retail, and banking stocks. The following sample information is collected.

Rate of Return

Utility       Retail     Banking

14.3          11.5        15.5

18.1          12.0        12.7

7.8          11.1          18.2

7.3          11.9           14.7

9.5          11.6            18.1

                                 13.2

a. Using the 0.05 level of significance, is there a difference in the mean rate of return among the three types of stock?

b. Suppose the null hypothesis is rejected. Can the analyst conclude there is a difference between the mean rates of return for the utility and the retail stocks? Explain.