ON DETERMINING THE NUMBER OF PREDICTORS IN A REGRESSION EQUATION USED FOR PREDICTION

It is generally recognized that all the available variables should not necessarily be used as predictors in a linear regression equation. The problems which may arise from using too many predictors become especially acute in a regression equation used for prediction with independent data. In this case, the skill of prediction may actually deteriorate with increasing numbers of predictors. However, there is no definitive explanation as to why this should be so. There is also no universally accepted procedure for determining the number of predictors to use. The various regression methods which do exist are logically contrived but are also largely based on subjective considerations.