Thank you Karen,

We could calculate the intrasubject CV.

There is another doubt.

For the calculation of intrasubject CV on four different days, the assumption is that the experimental set up is identical on all the four days. But in my case I'm doing four experiments on 4 different days over six months. By the virtue of the design of experiment, I have to expect a downward trend of the variable from day 1 - day 4. Is there any correction in Mixed model ANOVA, to account for this already expected downward trend. Downward trend can be calculated by taking means of all the 100 patients.

Thank you

Placebo.

www.clinpharm.********.com
Hi Placebo,

I have to say, I'm at the point of giving advice without being sure I exactly understand the experiment.

That said, if what you're saying is that you want to measure the intrasubject variability of a variable, which I will call DV, after accounting for the fixed and expected effect of Day, you would enter Day as a fixed effect in the model.

PROC Mixed;

CLASS Subid Day;

Model DV= Day;

RANDOM Subid;

run;

I realized I forgot the class statement in the previous code.

If you expect the effect of Day to be a linear downward trend, you would leave it out of the class statement. If you leave it out, it will be treated as continuous and the model will fit a slope. If you put it in the class statement, it will be treated as categorical, and the model will estimate the difference in means on the four days.

Can anyone else confirm my code?

Karen