The value of R2
is 0.656 showing that about 65.6%
of the total variation in Y can be explained by the three
independent variables. Finally, the value of D is 1.759.
We found that the value is significant at the 1% level.
This value shows that there is no autocorrelation
present in the error terms. The results suggest that the
model is fit and appropriate, thus it was selected for
final model validation.
From the previous analysis, we have reduced the
independent variables to a small number of three;
further study is focused on the study of interaction
effects. The residuals from regression Eq. 6 were
plotted against the pairwise interaction terms. None of
these plots suggests any need for a pairwise interaction
term in the regression model. In addition, a regression
model containing X1, X2 and X3 in first-order terms and
all two-variable interaction terms and the three-variable
interaction term was fitted: