Checking the Normality Assumption for an ANOVA Model

May 21st, 2012 by

I am reviewing your notes from your workshop on assumptions.  You have made it very clear how to analyze normality for regressions, but I could not find how to determine normality for ANOVAs.  Do I check for normality for each independent variable separately?  Where do I get the residuals?  What plots do I run?  Thank you!

I received this great question this morning from a past participant in my Assumptions of Linear Models workshop.

It’s one of those quick questions without a quick answer. Or rather, without a quick and useful answer.  The quick answer is:

Do it exactly the same way.  All of it.

The longer, useful answer is this: (more…)

Checking Assumptions in ANOVA and Linear Regression Models: The Distribution of Dependent Variables

April 10th, 2009 by

Here’s a little reminder for those of you checking assumptions in regression and ANOVA:

The assumptions of normality and homogeneity of variance for linear models are not about Y, the dependent variable.    (If you think I’m either stupid, crazy, or just plain nit-picking, read on.  This distinction really is important). (more…)