According to a genetics model, plants of a particular species occur in the categories A, B, C, and D, in the ratio 9:3:3:1. The categories of different plants are mutually independent. At a lab that grows these plants, 218 are in Category A, 69 in Category B, 84 in Category C, and 29 in Category D.

Question

Under the null, the expected number of plants in Category D is ______.

Degrees of freedom = _______.

Answer 1

Under the null, the expected number of plants in Category D is 25.
Calculation: 1/16 = x/400; x = 25
Note: 400 is the total number of plants in all categories.

Degrees of freedom = 3 (df = number of groups minus 1).