I want to test a mediation model, where IV and mediator are continuous and DV is a count variable. It was no problem to specify the model itself but unfortunately MPlus (6.1) cannot determine indirect effects when using count data (error: "BOOTSTRAP is not allowed with ALGORITHM=INTEGRATION."). Is there any workaround (f.e. with MODEL CONSTRAINT command), so I can test the assumed mediation effect formally?
Thank you for the quick response. I'm not sure if I did it correct, but I finally specified a constraint model with 4IV, 1 Med and 1 Count-DV (see below). Is this the way you thought of? If possible, I additionally want to determine the overall mediation effect (med_total). According to Preacher & Hays (2008) the total indirect effect is the sum of the specific indirect effects. Unfortunately, they used the bootstrap-procedure to analyze indirect effects and they had several mediators, not several IVs. Do you think I can still apply this rule to the current model (like I have done)?
Thank you very much, Sebastian
Title: Mediation with model constraints 4 IV, 1 Med, 1 DV (count)
Data: File is MPLUS3.dat ; Variable: Names are age sex type y2 y1 y3 x4 x1 x2 x3 m2 m1 sq2 sq3 sq1; usevariables are y1 m1 x1 x2 x3 x4; count is y1; analysis: estimator=ml; model: m1 on x1 (a1); m1 on x2 (a2); m1 on x3 (a3); m1 on x4 (a4); y1 on m1 (b); y1 on x1 x2 x3 x4; Model Constraint: new (med1 med2 med3 med4 med_total); med1 = a1*b; med2 = a2*b; med3 = a3*b; med4 = a4*b; med_total = med1+med2+med3+med4; output: samp; stdyx; tech1;