Moreover, multiple regression can also be used for the estimation of the significance of the independent variables.
the amount by which R 2 is reduced if a certain independent variable is deleted from the regression equation (in other words, the contribution of the independent variable to R 2) is represented by the squared semipartial correlation sri 2 (Tabachnick and Fidell 1996): where ti is the value of the t statistic for the ith variable and dffr¢~ are the residual degrees of freedom.