On 02/27/2013 03:13 PM, Kristina Nalbandian wrote:

Hello, I am running qdec group analysis on my patient data. I am studying the differences between two Epilepsy onset types and have a few questions.

1. I select "subtype" as my discrete variable and "duration" as my

continuous variable. In the display tab two questions appear. 1. Does the average thickness differ from zero? and 2. Does the average thickness differ between HYP and LVF (the two onset types)? What is the difference between these two questions? Mainly, can someone please explain question 1 and how that is calculated.

The first one is the mean across groups (not very interesting). The second is the one you are interested in.

2. Are corrections for multiple comparisons already build into the

qdec analysis? or is this something that needs to be run separately. Is permutation testing required to determine how likely the observed level of significant atrophy within each p-map would occur by chance?

You need to do something else. If you look on the bottom left of the display tab there should be some options (FDR and simulations of gaussian random fields). You can also run mri_glmfit-sim from the command line to give you the simulation with GRF and permutation. doug

Thank you in advance, Kristina

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