topic Interactions in factorial design in Statistical Procedures

Interactions in factorial design

DavidQ_R — Fri, 31 Aug 2012 08:18:19 GMT

Hi - I can specify a full factorial model with factors A, B, C and D in PROC GLM, PROC GLMSELECT etc using notation like this: A | B | C | D. But can I tell the procedure that I only want to include interactions of A, B, C and D upto and including the second order? Obviously I could write them all out in full (A*B A*C A*D B*C etc), but I'm guessing there's probably an easier way. Is there?

Many thanks.

Re: Interactions in factorial design

SteveDenham — Fri, 31 Aug 2012 12:00:01 GMT

There sure is. For your situation, use A|B|C|D@2. This will give a model with main effects and all two way interactions. In the documenation for GLM, look at Example 42.11 Analysis of a Screening Design, where they present a four factor model, and fit main effects and the two way interactions.

Steve Denham

Re: Interactions in factorial design

DavidQ_R — Fri, 31 Aug 2012 13:21:35 GMT

Perfect - just what I needed.

Many thanks!