Structural Equation Modeling

[#1]

@LauraCS 

Laura, I have a simple (hopefully) question.

I have two variables (x and y) that predict an outcome variable Z

The trouble is I think y depends on x

I'd like to set up a path analysis that shows me whether y has independent contribution to Z or is just serving as a proxy for x. When I do it the way I think I should, I don't get the answer I like ;)

Thanks you so much for your guidance - 

Tim Roberts, Professor of Radiology, CHOP

[#2]

@LauraCS Thanks, but empirically I don't think it should change the coefficients of FA-->M50 or GABA-->M50. The reason we see slight difference between a multiple regression model and a mediated model is very likely due to a small amount of missing data which may not (?) limit the multiple regression model, but would (?) limit the mediated model or the multiple regression model with curved arrow covariance. Does that sound possible ?

[#3]

I completely agree, Tim. I didn't notice you had missing data... that definitely explains the small differences!