Hello every body,
I'm trying to understand how does Glm works and I have not yet clear. I have already run Glm with 2 sample unpaired t-test and i think it works but now i have 4 groups and i'm confuse. Can anyone help me?
I have 4 groups to contrast FA values:
1.- Healthy (EV3)
2.- Disease 1 (EV1)
3.- Disease 2 (EV4)
4.- Disease 3 (EV2)
I want to contrast healthy controls vs diseases. The hypothesis is that FA decreases along the different groups (i.e. healthy control> disease1> disease2> disease3). Is that an one-way ANOVA 1 factor (with 4 levels: group)?. The steps in the design matrix were:
1) "Higher level/ not timeseries design"
- Select all the numer of subjects in "inputs" option.
- In the "Number of main EV's" option i select 4 (because of the 4 groups in the study. No covariates).
- Nothing in additional EV's.
- Then, the design matrix was carried out creating one EV for each group, each containing just 1s and 0s.
2) "Contrast and F-test"
I did 6 contrast -->
/ContrastName1 Healthy (EV3) > Disease1 (EV1)
/ContrastName2 Healthy (EV3) < Disease1 (EV1)
/ContrastName3 Healthy (EV3) >Disease2 (EV4)
/ContrastName4 Healthy (EV3) <Disease2 (EV4)
/ContrastName5 Healthy (EV3) >Disease3 (EV2)
/ContrastName6 Healthy (EV3) <Disease3 (EV2)
Matrix
EV1 EV2 EV3 EV4
-1.000000e+00 0.000000e+00 1.000000e+00 0.000000e+00
1.000000e+00 0.000000e+00 -1.000000e+00 0.000000e+00
0.000000e+00 0.000000e+00 1.000000e+00 -1.000000e+00
0.000000e+00 0.000000e+00 -1.000000e+00 1.000000e+00
0.000000e+00 -1.000000e+00 1.000000e+00 0.000000e+00
0.000000e+00 1.000000e+00 -1.000000e+00 0.000000e+00
I have not selected anything in the F-test option (i.e. F-test=0). Is that correct?
Then I saved the matrix.
Next, I have run randomise with this format:
randomise -i all_FA_skeletonised.nii -m mean_FA_skeleton_mask.nii -o resultados_TBSS -d matriz.mat -t matriz.con -n 5000 --T2 -V
Did I follow well all procedures? I appreciate very much your help.
Bests regards,
Patricia.
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