topic Re: Strip-split plot Interaction analysis in Statistical Procedures

Strip-split plot Interaction analysis

lcbeck — Wed, 09 Oct 2013 20:13:43 GMT

I am SAS illiterate and trying to finish my thesis (our departmental statistician retired). Having trouble collecting all necessary data for a strip-split plot. I need to analyze all of the main factors and their interactions. Previously, I was getting a minimum significant difference. Can anyone tell me if I am fully analyzing the data?

Whole plot factor: treatment

Strip: mowing

Split: timing

Random: rep

Based on information I found online and previous codes, this is what I've come up with:

proc glm data = visual;

class rep timing trt mowing;

model visual = timing|trt|mowing;

by MAT;

random timing|trt|mowing|rep;

lsmeans timing|trt|mowing / pdiff adjust=BON cl lines;

run;

Re: Strip-split plot Interaction analysis

SteveDenham — Thu, 10 Oct 2013 12:59:44 GMT

Stop. PROC GLM will not correctly calculate standard errors for split plot models. Do whatever it takes to get a copy of Littell et al.'s SAS for Mixed Models, 2nd ed., and go to chapter 4 on split-plot models. Also check out Chapter 16, which has case studies, especially 16.4 A Split-Plot Experiment with Correlated Whole Plots, 16.5 A Complex Split Plot: Whole Plot Conducted as an Incomplete Latin Square, and 16.6 A Complex Strip-Split-Split Plot Example.

Try rewriting your model using PROC MIXED. If you have problems, please post your code and the problems you are having.

Good luck.

Steve Denham