help > RE: directed network analysis
May 26, 2020  09:05 PM | Andrew Zalesky
RE: directed network analysis
Hi Greg,

this will depend on your design matrix. If column 1 models patients and column 2 models controls, then [1 -1] will test the alternative hypotheses that control are lower than patients. The opposite hypothesis will be tested for [-1 1].

This sign of the t-statistics will depend on your design matrix and contrast. 

As a sanity check, you can also consider one of the edges in the significant network and check that the average connectivity in each groups for that edge is in the right direction.

Andrew



Originally posted by Gregory Humble:
Hi Andrew,

I was wondering whether you could assist me in understanding the output from this directed version of NBS?

I am comparing directed connectivity values between two separate groups (the first group being individuals with Alzheimer's, and the second Controls).
The contrast I am using is [1 -1]. Am I right in understanding that any significant result would suggest that there is greater connectivity in individuals with Alzheimer's compared to Controls?


The reason I ask is that the directed script outputs a variable called test_stat_mat within which I assume are the t-statistics. However, in this instance, they are all negative values. My intuition is that the negative test statistic values show that in fact they have decreased connectivity (even though the contrast is [1 -1]).


Am I misinterpreting these results? 

Best regards,
Greg

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TitleAuthorDate
Jay Chen May 5, 2017
Andrew Zalesky May 5, 2017
Gregory Humble May 26, 2020
Andrew Zalesky May 26, 2020
Gregory Humble May 26, 2020
RE: directed network analysis
Andrew Zalesky May 26, 2020
Nikolas Chalas May 3, 2018
Andrew Zalesky May 3, 2018
Jay Chen May 5, 2017