Hello!

First, some background:

I've completed a ROI-to-ROI analysis with resting state data specifying 23 ROIs from the CONN atlas. In the second-level analysis, I want to test the association between my primary variable of interest (V1) and connectivity values within the ROI connectivity matrix, while also adjusting for 2 covariates (age and sex). I therefore have 4 subject effects in my general linear model, intercept (all subjects), V1, age and sex. My between-subjects contrast is [0 1 0 0] to test the main effect of V1.

When I go to Results Explorer, I define my connectivity matrix as "targets are source ROIs only", which gives me a 24x24 connectivity matrix (23 ROIs + the effect of rest). I further threshold ROI-to-ROI connections by intensity and use FDR analysis-level correction and enable permutation tests. As an example, I select the ACC as my seed ROI to see its connectivity to the other ROIs of interest and the relationship between the connections and V1. The test statistic for the ACC, overall, is F(4)(11) = 7.95, p-FDP = 0.0029.

My question: How are the df [F(4)(11)] generated for this f-test? It is the same regardless of how many seed ROIs I choose to view.

Thank you so much for any clarity that you can provide!

Best,
Allie