help > RE: calculating cohen's d from rZ values
Jan 7, 2015  02:01 PM | Patrick McConnell - MUSC
RE: calculating cohen's d from rZ values
Alfonso,

Thanks again for the thoughtful reply.  

For the initial seed-voxel bivariate correlations (step 1) and follow-up seed-voxel bivariate correlations (step 3/4), I generated the SPM.mat file using an F-test [1 0; 0 1] but then used t-contrasts to find the significant correlations (1, -1 and -1,1).  

In step 6, results (i.e., single subject regression coefficients) were used only to perform a within-group dependent samples t-test to determine whether there were statistically significant differences in magnitude of regression coefficient for each path (e.g., roi1 --> roi2 vs. roi2 --> roi1).  Denoised time-series were only used for visualization.   I understand why the Cohen's D will be biased for the follow-up seed-voxel bivariate correlations and the ROI-ROI bivariate regressions, but is there any issue of bias with the Cohen's D values calculated from the initial seed-voxel analyses (e.g., roi1a --> roi2a and roi1b --> roi2b)?  

We are basically seeing two separate paths, one of which seems to be strengthened in Tx group (roi1a path), and another that seems to be weakened in Tx group (roi1b path). Would it be valid to determine power/sample size for future studies based on these Cohen's D values?

Thanks again for sticking with me through this and being so generous with your replies.

All the best,
Patrick

Threaded View

TitleAuthorDate
Crystal Goh Jun 2, 2012
Alfonso Nieto-Castanon Jul 8, 2012
Patrick McConnell Dec 20, 2014
Alfonso Nieto-Castanon Dec 21, 2014
Patrick McConnell Dec 21, 2014
Alfonso Nieto-Castanon Dec 24, 2014
Patrick McConnell Dec 24, 2014
Patrick McConnell Jan 8, 2015
Alfonso Nieto-Castanon Dec 27, 2014
RE: calculating cohen's d from rZ values
Patrick McConnell Jan 7, 2015
Alfonso Nieto-Castanon Jan 15, 2015
Patrick McConnell Jan 22, 2015
Michael King Dec 16, 2014
Alfonso Nieto-Castanon Dec 17, 2014
Michael King Dec 17, 2014
Michael King Dec 17, 2014