

Identifying classes in LTA output 

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Anonymous posted on Monday, December 04, 2017  10:29 am



Hello, I have conducted an LTA with two time points, and I am having trouble interpreting the output. Specifically, I am not sure how to make sense of the following: FINAL CLASS COUNTS AND PROPORTIONS FOR THE LATENT CLASS PATTERNS BASED ON THE ESTIMATED MODEL Latent Class Pattern 1 1 957.85381 0.17867 1 2 655.26240 0.12223 1 3 305.38240 0.05696 2 1 238.98130 0.04458 2 2 781.94410 0.14586 2 3 958.19876 0.17874 3 1 37.27891 0.00695 3 2 225.37302 0.04204 3 3 1200.72529 0.22397 In addition, I am not clear on how to identify the classes in the Latent Transition matrix. I am concerned about class switching and subsequently ran the model with start values for the items in each model (model at Time 1 and model at T2),resulting in a slightly different transition matrix than when run without the starting values  yet, I am still not able to determine which classes are which. Any help would be greatly appreciated. 


You have a total of 3 x 3 = 9 classes. Call the class variables c1 and c2. The first 2 digits give the categories for c1 and for c2. The means/probabilities of the outcomes for different latent class variable categories is what give the categories meaning/interpretation. Using start values from the final estimates of a run with SVALUES is a good idea to avoid class switching  combine that with Starts=0 but check that you get the same best loglikelihood value. 

Anonymous posted on Tuesday, December 05, 2017  1:24 pm



Thank you, Dr. Muthen. 1. Just to be clear about the interpretation of the classes from the Pattern table, 1 1 for example, is prevalent at ~17.9%, which suggests that 17.9% of the sample is in category 1 at time 1 and in category 1 at time 2 (if the class variables are time)? 2. I have run the LTA with SVALUES, and now have start values. To avoid class switching then, do I need to include the start values for each indicator (item), and each category (3) for both class variables? I am not sure if this makes sense, but I am just not sure how to use the start values in the second run to avoid class switching. 


General comment: Be sure to listen to Topics 5 and 6 of our Short Courses on the website. 1. Right. 2. Yes in your first question. If the classes at time 2 are in a different order than the classes at time 1, you can use the SVALUES values for the indicators and rearrange them in the new order that you desire in order to give starting values that don't need Starts (but instead Starts=0). 

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