which interaction of the covariate in a model is considered to be of interest? what interaction is asked for in statistics how many interactions do you need to ask for in a model why are interaction models useful which interactions need to be asked in a model? does the main effect of the covariate need to be included in the model? can you ask for the main effect of a covariate which interaction is necessary to be included in a model? why is it important to ask for the main effect of a categorical variable when does the difference between covariate and categorical factor mean? does a model always include covariates which interaction to ask for in statistics do you have to ask for main effect of covariate in the model can you ask for interaction between variables in stats why should you ask for interaction does covariate interaction affect inference which interactions do you ask for in a model can you decompose covariate interaction in regression which factor must be factored away what interaction needs to be checked in a statistical process to determine a covariate effect