topic Mix procedures question in Statistical Procedures

Mix procedures question

Josue — Wed, 01 Jul 2015 15:06:40 GMT

Hi everyone,

I am having an issue how to account for the extra error term in our mixed statistical model using the SAS mixed procedure. I want to treat it as a split-plot design to come up with an ANOVA table, and one error term should not include the factor L (see equation below).

My guess is something like:

Proc Mixed data=StrainGauges method=type3; class rep F R C L;

model S=F R C FR FC RC FRC L FL RL CL FRL FCL RCL FRCL/ddfm=kr;

Random rep(A|B|C)

However, I am not sure how to write the random statement (e.g. "Random rep(A*B*C)" or "Random rep(A|B|C)"). Can someone help me to write this code?

Thanks in advanced!

Josue

Re: Mix procedures question

SteveDenham — Thu, 02 Jul 2015 19:30:15 GMT

This is a case where you have several random effects, so the rep(A*B*C) is obviously not what you need (and it is just as obvious that it is the residual error).

A much better approach would be:

random intercept F R C F*R F*C R*C F*R*C/subject=rep;

Also in your model statement, be sure to represent interactions with the '*' operator. As it is now, this would treat FR, FC, RC and FRC as continuous (and undefined) variables.

Steve Denham

Re: Mix procedures question

Josue — Fri, 03 Jul 2015 13:54:33 GMT

Thank you, Steve. Your comments will be very useful for our analysis!

Josue Bastos