= Obtaining covariance terms involving the intercept term in a linear regression using SPSS =
The covariance terms associated with the intercept (or constant) in SPSS obtained by firstly computing a column where every element equals 1.
{{{
COMPUTE CONST=1.
EXE.
}}}
The above created constant term may then be added as a predictor in, for example, a moderation analysis, after removing the default option to include the intercept (constant) in the analysis (using the /ORIGIN subcommand) and requesting the covariance matrix of the regression coefficients (using the /BCOV subcommand).
{{{
REGRESSION
/MISSING LISTWISE
/STATISTICS COEFF OUTS BCOV R ANOVA
/CRITERIA=PIN(.05) POUT(.10)
/ORIGIN
/DEPENDENT Y
/METHOD=ENTER CONST ZX ZM ZXM.
}}}