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Anonymous posted on Friday, September 05, 2003  5:28 pm



I am new to latent class analysis and I'm trying to running a 2 class model with 1 dichotomous and 3 3category variables. I'm not sure how to specify the starting values for the thresholds. I tried putting in some numbers ranging from 2 to 2. However, I keep getting an error message that says: "IN THE OPTIMIZATION, ONE OR MORE LOGIT THRESHOLDS APPROACHED AND WERE SET AT THE EXTREME VALUES. EXTREME VALUES ARE 15.000 AND 15.000." I've tried putting in different values, but have not been able to fix the problem. I'd appreciate any suggestions about what might be the source of the problem and how to fix it. Thank you! 


This is not a problem. It just means that in certain classes, certain items have either a probability of zero or one. This can help define the classes. 


We tried to change the reference class in a latent class analysis by entering starting values for the thresholds, but the reference class did not change. Even when we tried using extreme starting values the reference class did not change. We only succeeded by constraining the thresholds with the @ symbol. Do you know why this might have happened? Thank you very much for your help! 


Do you have STARTS=0; You may find using the STARTS option of the OUTPUT command useful. This gives the input with starting values and you can simply change the class numbers. 


We had random starts, but using STARTS = 0 solved the problem. Thanks for your help! 

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