In comparing the relation of company sales with GDP, your regression software provides the following output:

What must be the total number of observations for this study?

A. 88
B. 90
C. 91.

Correct Answer: C

Since the degrees of freedom of the residuals is measured as (n - k - 1) where n is the sample size and k is the number of independent variables, then: (N - 1 - 1) = 89: thus, N must be 91.