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 Lavinia Paternoster posted on Tuesday, November 13, 2012 - 9:41 am
I am trying to get a bootstrap p-value from my latent class analysis using the following commands:

LRTSTARTS = 40 8 40 8;
OPTSEED = 861413;
LRTBOOTSTRAP = 100;

But I am getting the following warning:

WARNING: THE BEST LOGLIKELIHOOD VALUE FOR THE 3 CLASS MODEL FOR THE GENERATED DATA WAS NOT REPLICATED IN 81 OUT OF 100 BOOTSTRAP DRAWS. THE P-VALUE MAY NOT BE TRUSTWORTHY DUE TO LOCAL MAXIMA. INCREASE THE NUMBER OF RANDOM STARTS USING THE LRTSTARTS OPTION.

Where 3 classes is the K-1 class model. In running the analysis without bootstrap and STARTS 40 8 the 3 (k-1) class model output looks ok (the best likelihood is replicated 8 times) - so what is going wrong in this bootstrap?

Also in all of the documentation I have seen, it is advised to use 0 0 in LRTSTARTS for the k-1 model - why is this the case? and what is going wrong in my case?

Thanks in advance
 Bengt O. Muthen posted on Tuesday, November 13, 2012 - 10:02 am
Web Note 14 might be helpful - you find it on our web site:

Asparouhov, T. and Muthén, B. (2012). Using Mplus TECH11 and TECH14 to test the number of latent classes. Mplus Web Notes: No. 14. May 22, 2012.
 Lavinia Paternoster posted on Tuesday, November 13, 2012 - 12:51 pm
I have consulted webnote 14 and followed the procedure for determining number of lrstarts for the k class model and for determining the OPTSEED.

I am confused because the warning I get refers to the k-1 generated data and according to webnote 14 the generated data are generated according to the k-1 model, so what could be going wrong for k-1 likelihoods in the generated data to not be replicated?
 Tihomir Asparouhov posted on Tuesday, November 13, 2012 - 5:19 pm
There is a typo in that error message. It should have been

WARNING: THE BEST LOGLIKELIHOOD VALUE FOR THE 4 CLASS MODEL FOR THE GENERATED DATA WAS NOT REPLICATED IN 81 OUT OF 100 BOOTSTRAP DRAWS. THE P-VALUE MAY NOT BE TRUSTWORTHY DUE TO LOCAL MAXIMA. INCREASE THE NUMBER OF RANDOM STARTS USING THE LRTSTARTS OPTION.

So try

LRTSTARTS = 0 0 150 40;
 Lavinia Paternoster posted on Wednesday, November 14, 2012 - 2:05 am
Thanks Tihomir, that worked fine.
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