Hi all, greetings from Argentina!
I wonder if anyone can enlighten me here. Let's suppose I have two groups and I ran some configural models and they were nearly ok but, inspecting modification indices, there is room for improvement if I make some adjustments.
For instance, a one-factor model with 10 variables (x1-x10) and two groups (a,b).
When I ran separately CFAs, it looks like x1-x3 residuals of these observable variables have to be correlated in the group a and no adjustments were needed for group b. Furthermore, once I checked x1 and x3´s meanings I found that both items refer to a similar construct in a way that group a (say, Spanish translated items) has an almost identical meaning--so we are good in thinking that there´s a theoretical reason to correlate those.
My question is how to model that (or, likewise, how to model when there are two different set, e.g., group a <- x1 ~~ x2, group b x3 ~~ x4)?? In Mplus I simply used to state different on each model and worked good (i.e., model a = x1 with x2 and model b = x3 with x4) , but can't find a way to do it in lavaan ...and it looks like I read a lot of material and didn' t find this issue. Of course, I'm talking in the context of measurement invariance analyses, I would need to merge both adjustments in a single configural model to start with the other invariance tests.
Thanks a bunch!
Instituto de Investigaciones
Universidad de Buenos Aires