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Anne Chan posted on Wednesday, December 29, 2010 - 2:47 pm
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Hello! I run a LPA on three variables. Comparing 1 to 3 classes solution, the 3 classes solution is the best and it works perfectly fine. However, when I go for the 4 classes solution. There is a error message: "THE STANDARD ERRORS OF THE MODEL PARAMETER ESTIMATES MAY NOT BE TRUSTWORTHY FOR SOME PARAMETERS DUE TO A NON-POSITIVE DEFINITE FIRST-ORDER DERIVATIVE PRODUCT MATRIX. THIS MAY BE DUE TO THE STARTING VALUES BUT MAY ALSO BE AN INDICATION OF MODEL NONIDENTIFICATION. THE CONDITION NUMBER IS -0.514D-18. PROBLEM INVOLVING PARAMETER 11. From the output file, I see that 1 group only have 1 case in it. May I ask what does this means? Is that the 4 classes solution does not fit the data? Can I still continue my project with the 3-class solution in this case? Thanks! |
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If your 4-class solution has its best loglikelihood value replicated several times so you believe you have reached the best maximum, then this 4-class solution is not useful and you should proceed with 3 classes. A 4-class solution like that can happen for instance if you let the variances differ across classes, but also in other cases. The one person is like an outlier. |
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Sandy lee posted on Monday, November 14, 2016 - 8:42 am
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Hello! Hope you are having a great time today. Anyhow, my question is about Latent Profile Analysis. I’m conducting LPA with one Social Anxiety Scale which has 5 factors. As I perform LPA to determine classes with the scale, profile comes out with high-medium-low classes. But when I perform it with either +1SD samples(N=76), or upper 25% samples(N=110) different and interesting pattern comes out. Thus, my question is, can I conduct LPA with either +1SD or upper 25% samples within one scale? Thank you so much for your time. I really appreciate it. Sincerely, Sandy |
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When you look at a subsample you can get more detail. But the variable distribution is different and the classes are affected by this so you have to have a strong substantive reason to focus on a subset. |
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Sandy lee posted on Monday, November 14, 2016 - 6:30 pm
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Thank you so much for the quick reply! I really hope to focus on subsample but I'm not sure how to provide a strong substantive reason. Please let me know if you know any study that focuses on subsample while doing LPA or a resource I can refer to. Again, thank you so much for your precious advice. Sincerely, Sandy |
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I can't think of a ref. right now - ask on SEMNET. Also check if it comes up in Lubke, G., Muthén, B., Moilanen, I., McGough, J., Loo, S., Swanson, J., Yang, M., Taanila, A., Hurtig, T., Jarvelin, M. & Smalley, S. (2007). Subtypes versus severity differences in the Attention-Deficit/Hyperactivity disorder in the northern Finnish birth cohort. Journal of the American Academy of Child and Adolescent Psychiatry, 46, 1584-1593. download paper contact first author show abstract |
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