In a regression analysis involving 27 observations, the following estimated regression equation was developed. y = 25.2

In a regression analysis involving 27 observations, the following estimated regression equation was developed.

yˆ = 25.2 + 5.5x1

For this estimated regression equation SST = 1550 and SSE = 520.

a. At α = .05, test whether x1 is significant. Suppose that variables x2 and x3 are added to the model and the following regression equation is obtained.

yˆ = 16.3 + 2.3x1 + 12.1x2 - 5.8x3

For this estimated regression equation SST = 1550 and SSE = 100.

b. Use an F test and a .05 level of significance to determine whether x2 and x3 contribute significantly to the model.