1. M

    Ancova interactions posthoc

    Hi everybody, I have a rather theoretical question about post hoc test in ancova with interactions. Suppose I have situation where I analyse the impact of x on y in 3 different groups (factor: group), like in the picture below. To do stats I use R. So I run a lm( y~ x * group) than I do...
  2. U

    Comparing results of a promotion camapign: Control vs Treatment Sub-Group

    I'm looking for some clarification on the correct way to test the difference between groups. At my company we ran a promotional campaign for credit card customers with a chance to win a prize. We took all customers who had a credit card and divided them into a Control Group and Treatment Group...
  3. S

    Orthogonal Contrasts

    What are orthogonal contrasts?