Bayes test of indirect effect in MSEM PreviousNext
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 Edward Lemay posted on Friday, October 02, 2015 - 7:53 pm
I am running a 2-level MSEM and want to test indirect effects using Bayesian credible intervals rather than the tests provided by MODEL INDIRECT because my understanding is that the MODEL INDIRECT tests, like Sobel tests, assume that the indirect effects are normally distributed over repeated sampling, and they can produce biased significance tests as a result. However, I also have equality constraints placed on some parameters. When I try to run the model, I receive this error:


*** FATAL ERROR
VARIANCE COVARIANCE MATRIX IS NOT SUPPORTED WITH ESTIMATOR=BAYES.
WITHIN A VARIANCE COVARIANCE BLOCK TWO OR MORE PARAMETERS ARE EQUAL.
ONLY FULL VARIANCE COVARIANCE BLOCKS WITH UNEQUAL PARAMETERS ARE ALLOWED.
USE ALGORITHM=MH TO RESOLVE THIS PROBLEM.

Algorithm=MH doesn't work for a two-level model.

Do you have a suggestion for how to obtains Bayes CIs for indirect effects in a 2-level MSEM featuring equality constraints?

Thank you!
 Bengt O. Muthen posted on Friday, October 02, 2015 - 8:31 pm
You can express the indirect effect in Model Constraint. This will give you the non-symmetric Bayes credibility intervals.

Model Indirect is expanded for Bayes in the upcoming Mplus version 7.4. It does not rely on normality assumptions for the indirect effect estimate distribution.

Regarding the Fatal Error message, please send input, output, data, and license number to Support.
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