Asymptotic covariance matrix of polyc... PreviousNext
Mplus Discussion > Categorical Data Modeling >
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 Jonathon Little posted on Wednesday, December 15, 2010 - 8:41 am
For categorical items using WLSMV I am running a multilevel factor model however there are some limitations to testing nested models, identifying sources of mispecification (etc) in a multilevel analysis and I wanted to output a within-level polychoric correaltion matrix and an asymptotic covariance matrix of the polychoric correlations. This is straignforward enough however where I would like some guidance is in regard to:

1. whether I should be using the polychoric correaltions matrix or the asymptotic covariance matrix as input for subsequent analysis, my thoughts are the latter; and

2. the most appropriate choice of estimator for the analysis of this within-level matrix.

Many thanks

JL
 Linda K. Muthen posted on Wednesday, December 15, 2010 - 5:16 pm
1. You cannot analyze the within polychoric correlation matrix and the asymptotic weight matrix in Mplus. You would need to analyze a multilevel model with an unrestricted model on between.

2. The default is WLSM.
 Elayne Livote posted on Friday, March 04, 2011 - 11:02 am
I am trying to run a confirmatory tetrad analysis (CTA) with ordinal indicators using the CTANEST1.SAS macro developed by Hipp, Bauer, & Bollen (2005). According to the instructions, the way to get the asymptotic covariance matrix of the polychoric correlations using Mplus is to run a saturated model using the WLS estimator model with no latent variables and allowing all the indicators to co-vary and then requesting and/or saving the Tech 3 output. These instructions (for Mplus version 2.1) were presumably provided by Dr. Muthen. However, everything Iíve read on the Discussion Board seems to indicate that you canít save the ACM using Mplus. Could you please clarify? Thank you very much.
 Linda K. Muthen posted on Friday, March 04, 2011 - 11:27 am
TECH3 is the asymptotic covariance matrix when a saturated model is used.
 Randall MacIntosh posted on Friday, December 28, 2012 - 8:32 am
I, too, am trying to obtain the ACM in a file. But the resulting tech3 output file from the savedata command is empty. The model terminates normally and I believe my model is saturated:

USEVARIABLES ARE X1-X5;
CATEGORICAL ARE x1-x5;
ANALYSIS: ESTIMATOR IS WLS;
MODEL:
x1-x4 with x5;
x1-x3 with x4;
x1-x2 with x3;
x1 with x2;
Savedata:
tech3 is year92_5.acm;
 Linda K. Muthen posted on Friday, December 28, 2012 - 8:53 am
Please send your output and license number to support@statmodel.com.
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