I am asked in G*Power to enter the Correlation among repeated measures. I have repeated an experiment with the same subjects under 3 conditions (Set1, Set2 and Set3).
I calculate the correlation this way:
lala=cbind( Set1.Weber, Set2.Weber, Set3.Weber ) cor(lala)
Set1.Weber Set2.Weber Set3.Weber Set1.Weber 1.0000000 0.3683676 0.1283023 Set2.Weber 0.3683676 1.0000000 -0.0959547 Set3.Weber 0.1283023 -0.0959547 1.0000000
as a result.
Is that correct? In G*Power there is only one parameter for the correlation. Should I use the average correlation. In the example:
Here is a screenshot:
Edit: As a response to the very good answers so far I want to specify the question:
Do I understand that correct that the ANOVA assumes that the correlation should be equal in the matrix and not like in my case (3 different values)? So it maybe not super correct but I can use an average as a poormans solution?! I could use (|a|+|b|+|c|)/3 or sqrt(a²+b³+c²)?!