12.6 Ages of customers at different coffeehouses. In Example 12.2 (page 645) the ages of customers at different coffeehouses are compared, and you described the ANOVA model for this study in Exercise 12.4 (page 653). Here is a summary of the ages of the customers:
| Store | s | n | |
|---|---|---|---|
| A | 38 | 8 | 50 |
| B | 48 | 13 | 50 |
| C | 42 | 11 | 50 |
| D | 28 | 7 | 50 |
| E | 35 | 10 | 50 |
(a) Is it reasonable to pool the standard deviations for these data? Explain your answer.
(b) For each parameter in your model from Exercise 12.4, give the estimate.