Back to PLS HelpPosted on 12/11/13 09:57:49
Number of posts: 26
Dear PLS experts,
I have a block design fMRI task with two conditions (self and other referential processing) for two groups. Task PLS mean centering on these data identified one significant LV reflecting the following profile (contrast) self vs other in both groups. Is this reflecting the mean effect or the group conjunction effect?
Can anybody explain why it is one or the other?
Many thanks,
Mohamed
Replies:
Posted on 12/11/13 15:19:49
Number of posts: 394
Dear PLS experts,
I have a block design fMRI task with two conditions (self and other referential processing) for two groups. Task PLS mean centering on these data identified one significant LV reflecting the following profile (contrast) self vs other in both groups. Is this reflecting the mean effect or the group conjunction effect?
Can anybody explain why it is one or the other?
Many thanks,
Mohamed
If by group conjunciton you mean where the effect between self vs other is the same for both groups, then yes its more of a conjunction. In the terminology of analysis of variance, its more like it the main effect of self vs other, whereas the interaction of group X self vs other appears to not be significant given that only the main effect is significant.
Posted on 12/12/13 06:21:33
Number of posts: 60
If by group conjunciton you mean where the effect between self vs other is the same for both groups, then yes its more of a conjunction. In the terminology of analysis of variance, its more like it the main effect of self vs other, whereas the interaction of group X self vs other appears to not be significant given that only the main effect is significant.
Hi Mohammad,
We have a recent paper in which task PLS with 2 conditions across two groups was used! You may want to take a look at it to see how we interpret the results! You should also be careful about how the mean-centering is going to be carried out (i.e. across two groups vs. within each group). This has been taken care of in the latest version of PLS.
Salami, A., Rieckmann, A., Fischer, H., and Backman, L. (2013). A Multivariate Analysis of Age-Related Differences in Functional Networks Supporting Conflict Resolution. Neuroimage.
Hope it helps!
/Alireza
Posted on 12/17/13 08:06:34
Number of posts: 26
If by group conjunciton you mean where the effect between self vs other is the same for both groups, then yes its more of a conjunction. In the terminology of analysis of variance, its more like it the main effect of self vs other, whereas the interaction of group X self vs other appears to not be significant given that only the main effect is significant.
Many thanks for your answer!
Mohamed
Posted on 12/17/13 08:09:18
Number of posts: 26
Hi Mohammad,
We have a recent paper in which task PLS with 2 conditions across two groups was used! You may want to take a look at it to see how we interpret the results! You should also be careful about how the mean-centering is going to be carried out (i.e. across two groups vs. within each group). This has been taken care of in the latest version of PLS.
Salami, A., Rieckmann, A., Fischer, H., and Backman, L. (2013). A Multivariate Analysis of Age-Related Differences in Functional Networks Supporting Conflict Resolution. Neuroimage.
Hope it helps!
/Alireza
Thanks a lot for your kind answer!
Mohamed
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