help > RE: 2x3 Mixed Design ANOVA
Oct 10, 2018  03:10 PM | Andrew Zalesky
RE: 2x3 Mixed Design ANOVA
Hi Ana,

your design matrix appears to be correct. I don't see any errors.

However, in the case of three time points, you may want to test a specific hypothesis such that connectivity strictly increases (or decreases) with time: time1 < time2 < time3. This will afford greater power than testing the general case in which all combinations are possible. While I am not familiar with your application, there may be some sequences (e.g. time2 > time3 > time1) that are not realistic to test and shoud therefore be excluded a priori.

Remember to include exchange blocks, given that your design appears to be repeated measures.

To test the main effect of time, the contrast for an F-test would be: [1 1 0 0 0.....]

Andrew


Originally posted by Ana Coelho:
Hi Dr. Zalesky,

I would like to do a 2x3 mixed ANOVA analysis and I was hoping that you could confirm that my design matrix is correct.
So, I have two groups (good and bad cognitive performers) and they were evaluated at 3 timepoints. I want to evaluate the interaction group x time

My data is organized as follows:
good1-time1
good1-time2
good1-time3
good2-time1
good2-time2
good2-time3
...
bad1-time1
bad1-time2
bad1-time3
bad2-time1
bad2-time2
bad2-time3
...

The design matrix for an example with 4 subjects will be something like this:
1 0 1 0 1 0 0 0
0 1 0 1 1 0 0 0
0 0 0 0 1 0 0 0
1 0 1 0 0 1 0 0
0 1 0 1 0 1 0 0
0 0 0 0 0 1 0 0
1 0 -1 0 0 0 1 0
0 1 0 -1 0 0 1 0
0 0 0 0 0 0 1 0
1 0 -1 0 0 0 0 1
0 1 0 -1 0 0 0 1
0 0 0 0 0 0 0 1

where the first 2 columns model time. columns 3 and 4 model interaction and last 4 columns the subject means. 
Is this design correct? 

Thanks in advance!
Best regards,
Ana

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Ana Coelho Oct 10, 2018
RE: 2x3 Mixed Design ANOVA
Andrew Zalesky Oct 10, 2018
Ana Coelho Oct 11, 2018
Andrew Zalesky Oct 11, 2018
Ana Coelho Oct 12, 2018
Andrew Zalesky Oct 15, 2018
Ana Coelho Oct 15, 2018
Andrew Zalesky Oct 15, 2018
Ana Coelho Oct 18, 2018
Andrew Zalesky Oct 18, 2018
Ana Coelho Oct 19, 2018