
Message/Author 

aguri posted on Monday, November 19, 2012  10:04 pm



Dear Dr. Muthen I am using MPLUS 3.11 to run a Latent Class Analysis. The database are from TIMSS 2007 about student attitudes to math, 12 items(Likert 4point) and about 4000 test takers included.I try to make exploratary LCA to find how many classes would be approriate, two questions are bumped into: 1. the pvalue of Likelihood Ratio ChiSquare from c(1) to c(3) are 1, when c(4), something showed up... THE MODEL ESTIMATION DID NOT TERMINATE NORMALLY DUE TO A NONPOSITIVE DEFINITE FISHER INFORMATION MATRIX. CHANGE YOUR MODEL AND/OR STARTING VALUES. ....... so I try to recode the data from 4point to 2 categories (positive and negative orientation),and the result showed 5 classes is much better. I am not sure what happened when 4point situations, and could I deal with the problem as description !!??(Do you recommend to change estimates method or setting starting value!?) 2. If I want to know which class level each test taker belongs to, what can I do !!?? THANKS A LOT my code as reference ~ TITLE: LCA DATA: FILE IS test1115.dat; VARIABLE: NAMES ARE gender i1i12 ; USEVARIABLES ARE i1i12; CLASSES = c (3); CATEGORICAL = i1i12; ANALYSIS: TYPE = MIXTURE; OUTPUT: TECH1 TECH7; 


The two chisquare statistics given for the frequency tables of the categorical variables are not useful when you have more than about 8 variables. You should ignore these. You should not recode your data. You should use more starts, for example, 1000 250. 


My LCA model returned a nonsignificant p value for the 4 class model, but the 3 class model seems to have identification problem. I increased the random starts to (1000 100), and the best loglikelhood replicated twice, but it displayed this error. THE STANDARD ERRORS OF THE MODEL PARAMETER ESTIMATES MAY NOT BE TRUSTWORTHY FOR SOME PARAMETERS DUE TO A NONPOSITIVE DEFINITE FIRSTORDER DERIVATIVE PRODUCT MATRIX. THIS MAY BE DUE TO THE STARTING VALUES BUT MAY ALSO BE AN INDICATION OF MODEL NONIDENTIFICATION. THE CONDITION NUMBER IS 0.181D16. PROBLEM INVOLVING THE FOLLOWING PARAMETER: Parameter 4, %C#1%: [ PERC_CASH ] What does this error mean? And how do I fix it? Or does it suggest that I should move to the 2 class model instead? 


Please send the output and your license number to support2statmodel.com. 

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