why do you need a contrast matrix which is the only level of interaction between A & b which contrast is an interaction do you need the contrast matrix in a glm how to test if a factor is a significant interaction between two factors based on an orthogonal contrast how many levels to test the significance of a factor in a binary how many treatments are needed for an interaction of a factor in glm how many treatments in contrast how many levels for a contrast how many levels in a glm do you need to construct an orthogonal matrix for one contrast glm contrast matrix examples why does contrast need a matrix? what is the ratio between contrast and interaction what is the correlation between factors in a glm how to show difference between two factor comparisons in lp why use an orthogonal contrast matrix how many levels can be constructed in a matrix why does a glm matrix need to be built with one contrast which factor has the highest correlation coefficients