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Hi, We are attempting to test 211 mediation using DSEM and could use some guidance on code construction. We are using timevarying EMA data on mood and smoking for m and y. X is a timeinvariant measure of SES for 375 participants. My primary question is what it means for interpreting the ab path to also have y on m estimated at the Between level in DSEM. Preacher’s 211 models have this path whereby the within b path is added to the between b path before multiplying ab. Thanks so much. %WITHIN% s_my  y on m; ! L1 b path phi  y on y&1; ! L1 control for autoreg y m; ! L1 residual variances %BETWEEN% x m y; ! L2 residual variances s_my WITH phi y m; ! covariances phi WITH y m; y WITH m; [phi]; ! L2 autoreg mean [s_my] (bw); ! L2 b path mean y on x (c); m on x (a); y on m (bb); ! What would this path mean in DSEM? MODEL CONSTRAINT: NEW (ab); ab=a*bw; 


The answer to this is a bit involved  we'll get back to you shortly. 


I would refer you to Appendix F in https://www.statmodel.com/download/Preacher.pdf for understanding and interpreting the model. The bb parameter is the most straight forward to interpret, it is the bw parameter that requires insight. If you are using DSEM then you need to understand the sentence containing equation (61) in http://statmodel.com/download/DSEM.pdf From there using plausible values you need to compute bw=E(s_my/(1phi)). That is the only way unfortunately such an expectation is generally undefined for two normal random effects. In the next Mplus version we will have some of these steps simplified. 


A great first step would be to simplify the model by replacing phi  y on y&1; with y on y&1 (phi); In many case Var(phi) is too small anyway so it would not be detrimental to assume the same autocorrelation across subjects. In that case the indirect effect is simplified substantially and you can simply use MODEL CONSTRAINT: NEW (ab); ab=a*(bb+bw/(1ph)); 


Great. Thank you for the help! 

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