I have a study looking at Intervention vs Control on disability. The secondary analysis of the study is looking at the subgroup of people who are taking Vit D supplementation measured at baseline let's say.
Based on regression, we have three effects:
1. Main Effect of Vit D vs No Vit D on subjects in both intervention and control group combined.
2. Main Effect of treatment vs No treatment in both treatment and control group combined
3. Interaction Effect of Vitamin D on the treatment (interaction effect)
Main effects were significant, but the interaction was not. Can we still conclude that Vit D is associated with lowered risk of disability, but do not modify the effect of treatment?
Thank you
Anoop
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