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ANKH1
Pyrite | Level 9

Hello, 

 

We are designing a cross-over repeated measures design. Participants will have all 4 treatments at four different sessions days. During each session, samples will be collected over several time points for 2 hrs. There will be a washout period between sessions. 

Is there a SAS procedure for such calculation?

 

Thank you!

3 REPLIES 3
sld
Rhodochrosite | Level 12 sld
Rhodochrosite | Level 12

You can use the GLIMMIX procedure for this purpose. See PROC GLIMMIX as a Teaching and Planning Tool for Experiment Design.

 

I hope this helps.

 

ANKH1
Pyrite | Level 9

Thanks. Although a good read it doesn't address power calculation for crossover designs. Is there another article you recommend that addresses this calculation?

sld
Rhodochrosite | Level 12 sld
Rhodochrosite | Level 12

The design planning process described in Stroup's paper works for any statistical model that you can specify using either the MIXED or GLIMMIX procedures. So if you can write a statistical model for your crossover design, then you can estimate sample sizes for specified exemplary datasets. That's the beauty of this approach: it can deal with a wide variety and complexity of statistical models. Although, of course, the process gets more involved as the statistical model gets more complex.

 

I do not know of any papers describing this process for a crossover design, but that does not mean that there are none. I suggest starting simply, with "subsets" of your design--for example, an assessment of sample size for just the first period if you have replicate subjects--and then build from there.

 

I hope this helps.

 

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