@atorchio wrote:
Hello! I need to perform a one-way ANOVA once using effect coding and once using reference coding for a categorical variable with four categories.
I suppose you can do this in PROC GLM, but the two models are identical — the predicted values are the same, the fit is the same.
@atorchio wrote:
However, I noticed that PROC GLM only allows reference coding...
You could create your own effect coding dummy variables in a DATA step and then use these dummy variables in PROC GLM, but the end result is the same. In fact, this is one of the major benefits of PROC GLM (and other SAS modeling PROCs) is that you don't have to spend the time to create your own dummy variables for categorical effects (and potentially make mistakes), SAS does this for you behind the scenes.
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