The number of observations minus the number of parameters in a regression analysis It is sensible to include all variables considered for use in the model, not just those in the final version. The larger the number of coefficients estimated, the larger the number of constraints imposed in the sample and the smaller the number of observations left to provide precise estimates of the regression coefficients. A greater number of degrees of freedom is often thought to provide more reliable estimates, but the relationship to reliability is weak. (See adjusted R2.)