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Re: Compare correlations between 3 groups

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Wed, 31 May 2017 14:58:45 +0100

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 ```Dear Mike, your contrasts look fine assuming that the first 3 columns are the group factors. Additionally, you can also use in a first step a contrast for the F-test to test whether there are any differences between the correlations of the 3 groups: [zeros(n,n) eye(n)-1/n] where n is the number of groups. This results in:          0 0 0 0.6667 -0.3333 -0.3333          0 0 0 -0.3333 0.6667 -0.3333          0 0 0 -0.3333 -0.3333 0.6667 Best, Christian On Mon, 22 May 2017 13:21:59 +0100, Mike <[log in to unmask]> wrote: >Hi, > >I have 3 groups (group 1-3) with n=10 in each group, and I want to know brain activity showing different between-group correlations with age during a task period. I select Full Factorial, 1 factor ("group"), 3 levels, then specify cells for the 3 groups by order. In Covariates, I input: > >Covariate 1: 10 age numbers of group 1, then 20 zeros >Covariate 2: 10 zeros, then 10 age numbers of group 2, then 10 zeros >Covariate 3: 20 zeros, then 10 age numbers of group 3 > >In contrast setting, for example, > >Correlation (group 1>2): 0 0 0 1 -1 0 >Correlation (group 2>3): 0 0 0 0 1 -1 > >Am I correct? > >Thanks >Mike ```

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