You can estimate , the intercept, and , the slope, in for the observations . Fitting this model with the REG procedure requires only the following MODEL statement, where y is the outcome variable and x is the regressor variable. between the two slopes divided by the standard error of the difference between the slopes, that is, 1 2 1 2 s b b b b z If your regression program gives you the standard error of the slope (both SAS and SPSS do), the standard error of the difference between the two slopes is most easily computed as .08140 .095942.1258 1 2 1 2 s b b s b s b .