Let's say there's one DV (Y
) and three IVs (X1
, X2
, X3
), and among IVs, X1
is a dummy variable.In the regression model without interaction terms, the results can be represented like this:
Y ~ X1 + X2 + X3X1 : non-significantX2 : significantX3 : significant
In this case, is it meaningful to check some interaction terms (e.g. X1
$\cdot$ X2
or X1
$\cdot$ X3
)? At first I thought I don't have to because the main effect of X1
indicates non-significance. But I'm afraid I'm missing something important.