what is valid to include interaction terms but leave main effects out? why is it valid to exclude main effects in a regression? when to exclude the main effects from the main effect why are interactions and main effects excluded why is interaction terms valid why is the interaction term in regression valid why are interaction terms and main effects excluded from a regression can you exclude interaction in the regression what is the problem if you exclude all main effects and interaction terms can you leave interaction terms out why should you leave interaction terms out is it valid to exclude major interaction which term excludes main effects why are main effects and interaction terms insignificant in social science is interaction terms valid how are main effects excluded from the main effect? why is if an interaction term is excluded main effect why are interaction terms considered in regression is it valid to include interactions and main impacts and exclude them all? which term is useful to exclude all interaction terms?