The correct way to do this is described in the following paper which is available on the website:
Muthén, B. (2011). Applications of causally defined direct and indirect effects in mediation analysis using SEM in Mplus.
Your input using WLSMV is an approximate way to do this.
Wen-Hsu Lin posted on Tuesday, November 26, 2013 - 9:13 pm
In the paper for nominal mediator.Does the threshold for a particular class indicate the relationship between that particular group and the outcome variable?
Wen-Hsu Lin posted on Wednesday, November 27, 2013 - 12:54 am
Sorry, another related but simple question. My first post model, the correlation between m12 and m13 is very high in Mplus output. However, it is only moderate when I use SPSS to estimate this same correlation. Where did I do wrong?
I don't know what you mean by your first question. Regarding the m12, m13 correlation, note that there are two kinds of correlations for binary variables: Tetrachorics and Pearson. You may be looking at the former in Mplus and the latter in SPSS.
Wen-Hsu Lin posted on Wednesday, November 27, 2013 - 9:24 pm
Is the threshold represents the impact of a particular known class on outcome variable?