An analyst is estimating a regression equation with three independent variables, and calculates the R2, the adjusted R2, and the F-statistic. The analyst then decides to add a fourth variable to the equation. Which of the following is most accurate?
A) |
The R2 and F-statistic will be higher, but the adjusted R2 could be higher or lower. | |
B) |
The adjusted R2 will be higher, but the R2 and F-statistic could be higher or lower. | |
C) |
The R2 will be higher, but the adjusted R2 and F-statistic could be higher or lower. | |
The R2 will always increase as the number of variables increase. The adjusted R2 specifically adjusts for the number of variables, and might not increase as the number of variables rise. As the number of variables increases, the regression sum of squares will rise and the residual T sum of squares will fall—this will tend to make the F-statistic larger. However, the number degrees of freedom will also rise, and the denominator degrees of freedom will fall, which will tend to make the F-statistic smaller. Consequently, like the adjusted R2, the F-statistic could be higher or lower. |