15.30 Four financial analysts were asked to predict earnings growth over the coming year for five oil companies.

Their forecasts, as projected percentage increases in earnings, are given in the accompanying table.

a. Prepare the two-way analysis of variance table.

b. Test the null hypothesis that the population mean growth forecasts are the same for all oil companies.

Analyst Oil Company A B C D 1 8 12 7 13 2 9 9 8 12 3 12 10 9 10 4 11 10 10 12 5 9 8 10 14