Fertilizing Bromeliads

Bromeliads are tropical flowering plants. Many are epiphytes that attach to trees and obtain moisture and nutrients from air and rain. Their leaf bases form cups that collect water and are home to the larvae of many insects. As a preliminary to a study of changes in the nutrient cycle, Jacqueline Ngai and Diane Srivastava examined the effects of adding nitrogen, phosphorus, or both to the cups. They randomly assigned 8 bromeliads growing in Costa Rica to each of 4 treatment groups, including an unfertilized control group. A monkey destroyed one of the plants in the control group, leaving 7 bromeliads in that group.

Here are the numbers of new leaves on each plant over the seven months following fertilization:

| Nitrogen | Phosphorus | Both | Neither |
|----------|------------|------|---------|
| 15 | 15 | 14 | 14 |
| 14 | 17 | 18 | 19 |
| 18 | 13 | 14 | 11 |
| 16 | 13 | 15 | 16 |
| 14 | 14 | 15 | 13 |
| 11 | 17 | 14 | 15 |
| 13 | 12 | 15 | 15 |

(a) Give the degrees of freedom for the F statistic:
- Numerator degrees of freedom
- Denominator degrees of freedom

(b) Find the F-statistic. (Round your answer to two decimal places.)

(c) Find the associated P-value. (Round your answer to four decimal places.)