sdm-help-list > Interpreting linear model results - comparing two groups
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Nov 7, 2022  04:11 PM | Molly Rowlands
Interpreting linear model results - comparing two groups
Hi, 

I've conducted a comparison of two meta-analyses, group A = 0, group B = 1, yielding the 1m0 "differences" map. 

From reading the literature + this forum, I was under the impression that this 1m0 "differences" map showed regions that are more active in group A (set as 0) than in group B (set as 1). However, when comparing this 1m0 "differences" map to the individual meta-analytic maps for group A and B, the 1m0 map appears more like the individual map for group B, rather than for group A. (If 1m0 represents regions more active in group A, then I would expect the opposite, i.e. that it would like more like group A's individual meta-analytic map) Conversely, the 1m0_neg map - which I thought showed regions of less activation in Group A (set as 0) compared to Group B (set as 1) - appears more similar to the individual meta-analytic maps of Group A. (Again, If 1m0_neg represents regions less active in group A, then I would expect the opposite, i.e. that it would less like group A's and more like group B's individual meta-analytic maps) As a result of this I'm doubting my interpretation above and wanted to clarify. 

To summarise, if group A is set to 0, and group B set to 1, does the 1m0 and represent regions that are more active in group B, set as 1 (compared to group A, set as 0)? Similarly, does the 1m0_neg map represent regions more active in group A compared to group B?

Thank you! 

Best, 
Molly
Nov 8, 2022  04:11 PM | Lydia Fortea - Instituto de Investigaciones Biom├ędicas August Pi i Sunyer (IDIBAPS)
RE: Interpreting linear model results - comparing two groups
Dear Molly, 

The 1m0 differences showed the higher "activation" (measure you are studying) in the group you set as 1 in that variable in comparison with 0.
In your case, 1m0 will showed the regions significant for B>Am and 1m0_neg for B
Hope it is clear now, 
Kind regards, 
Lydia
Nov 8, 2022  07:11 PM | Molly Rowlands
RE: Interpreting linear model results - comparing two groups
Hi Lydia, 

That's great - thank you!