

LCA: help interpreting output/errors 

Message/Author 

Brian Hall posted on Tuesday, September 21, 2010  5:27 am



Performing a LCA on a sample of 350 with 4 measures. Please help in interpreting these error messages. Also please provide a simple explanation for the application of random starts. Brian 1: IN THE OPTIMIZATION, ONE OR MORE LOGIT THRESHOLDS APPROACHED AND WERE SET AT THE EXTREME VALUES. EXTREME VALUES ARE 15.000 AND 15.000. THE FOLLOWING THRESHOLDS WERE SET AT THESE VALUES: * THRESHOLD 1 OF CLASS INDICATOR var1 FOR CLASS 2 AT ITERATION 7 * THRESHOLD 1 OF CLASS INDICATOR var1 FOR CLASS 3 AT ITERATION 11 * THRESHOLD 1 OF CLASS INDICATOR var1 FOR CLASS 1 AT ITERATION 19 * THRESHOLD 1 OF CLASS INDICATOR 2: 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 0.174D14. PROBLEM INVOLVING PARAMETER 4. 3) ONE OR MORE MULTINOMIAL LOGIT PARAMETERS WERE FIXED TO AVOID SINGULARITY OF THE INFORMATION MATRIX. THE SINGULARITY IS MOST LIKELY BECAUSE THE MODEL IS NOT IDENTIFIED, OR BECAUSE OF EMPTY CELLS IN THE JOINT DISTRIBUTION OF THE CATEGORICAL LATENT VARIABLES AND ANY INDEPENDENT VARIABLES. THE FOLLOWING PARAMETERS WERE FIXED: 19 


1. This is not a problem. It means that the thresholds are high reflecting probabilities of 0 (+15) and 1 (15). This can be helpful in defining the classes. 2. You would need to send the output and your license number to support@statmodel.com for this. The meaning can vary. 3. This is usually because in one class the covariate has no variability but I would have to see it to be sure. 

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