Help With Analysis for Replicated Latin Square Design containing nested data and repeated measures

ChKayAb — Sun, 25 Feb 2024 18:20:44 GMT

I'm having trouble debugging my analysis.

Am I using the right procedure?

I designed a Latin square observational experiment that was replicated for 3 years.

3 new colonies were assigned to each farm each year, and I had 3 farms in each of my 3 treatments.

Colonies are my sub replicate (nested in farm).

I then measured colony weight weekly.

However, my data is not entirely complete.

In year 1, I only have measurements for weeks 1, 5, 9, and 13.

In year 3, I only assigned 2 colonies to each farm.

I've managed to come up with the below model. However, my results don't show a test statistic for Treatment effect.

Can you tell me if I'm using the right procedure and is my model is incorrect?

proc mixed;
class Treatment Colony Farm Year Week Weight;
model Weight = Treatment Week Treatment*Week Treatment*Year Treatment*Week*Year Farm Year Week / ddfm=kr;
random int / subject=Colony(Farm);
random int / subject=Year;
repeated week / subject=Treatment(Colony Farm Year) type=ar(1);
run;

Re: Help With Analysis for Replicated Latin Square Design containing nested data and repeated measur

SteveDenham — Wed, 28 Feb 2024 13:10:07 GMT

This is a "not sure if it will work" answer, but the degrees of freedom look a bit wonky, and it is probably because you are using the Kenward-Roger denominator degrees of freedom with a very sparse dataset due to the missing values.

Try, in order, ddfm=satterthwaite, ddfm=bw, or using ddf= with fixed values based on a skeleton ANOVA table. You could then add in an EMPIRICAL option to get the shrinkage estimates.

SteveDenham

topic Re: Help With Analysis for Replicated Latin Square Design containing nested data and repeated measur in Statistical Procedures

Help With Analysis for Replicated Latin Square Design containing nested data and repeated measures

Re: Help With Analysis for Replicated Latin Square Design containing nested data and repeated measur