If you don't exactly know how your classes move across time but you are pretty sure that they do in fact transition, would it possible to examine a saturated LTA model using a random half of your sample? Then, take the significant paths and confirm this model with the random second half of the sample?
If you have a large enough sample, you could randomly split it and do the analysis in both halves to see if you get the same results. I would not fix any parameters.
Lucy Barnard posted on Saturday, September 01, 2007 - 3:46 pm
Is there any way to do multiple latent class analyses within the same model and then compare the results? I basically want to see if the latent class structure I observe at the first time point is stable across time.
As a first step in a latent transition analysis, you should do a latent class analysis for each timepoint to see how many classes fit the data at each timepoint. The dissertation on the website by Karen Nylund describes the steps to take to carry out a latent transition analysis. I suggest taking a look at it.
I not sure if this is a crazy question or not, but here it is. First let me say that I have cross-sectional data, but the questionnaire that Iím looking at asked participants to respond to questions related to their past body weight and physical activity behavior at multiple time points (e.g., age 20 to 25, age 15- 20). As expected this data also asks questions about current behavior. Can I use LTA to determine how participants transition from old health behavior to their current behavior? Again, sorry but Iím really not sure. Thanks
I think so, with the usual caveat about "telescoping effects".
Julia Lee posted on Saturday, June 02, 2012 - 6:25 pm
Hi Dr. Muthen,
I am using LTA mover-stayer modeling for continuous variables. Is it possible for movers to "move" within the same class for a LTA mover-stayer modeling for continous variable?
The mover and stayer means for my output are different. For 1 1 1 (movers class 1 class 1), the class count is 98.54, proportion is .18. The essential question is whether the 98 students moved (since they are classified as movers) within the same class and mixture modeling in Mplus decided that they had only "moved" within a particular threshold. Did the students make just enough improvements to remain in Class 1 but did not move to Class 2 because of a particular threshold? Conceptually, wouldn't this type of movers (e.g. 1 1 1) be considered "movers who moved within the same class" and aren't they (logically) portraying the actual stability of group membership even though 69% of the students were classified as movers? 1 1 1 98.54240 0.18914 1 1 2 0.00000 0.00000 1 2 1 56.89545 0.10920 1 2 2 162.25686 0.31143 2 1 1 56.41806 0.10829 2 1 2 0.04694 0.00009 2 2 1 0.00487 0.00001 2 2 2 146.83542 0.28183
It doesn't look like your results for movers (first class=1) indicate that they behave like movers since most stay in the same class (classes 1 1 1 and 1 2 2 are the most frequent). You don't move if you stay in the same class over time.
Julia Lee posted on Sunday, June 03, 2012 - 1:00 am
So the classes 1 1 1 and 1 2 2, although being classified as "movers," were conceptually stayers? Then they are not any different from the stayers (i.e., Classes 2 1 1 and 2 2 2). Is it possible to have a large number of classified as movers (61%) yet, they are 1 1 1 or 2 2 2? Did I miss something? I appreciate your insight. Thank you very much.
FINAL CLASS COUNTS AND PROPORTIONS FOR EACH LATENT CLASS VARIABLE BASED ON THE ESTIMATED MODEL Latent Class Variable Class
Well, you have 10.9% in 1 2 1, so those people are moving. It is the 0% in 1 1 2 that don't want to move - perhaps going from 1 to 2 is a hard transition to make (an example would be knowing less at time 2 than at time 1). I assume that you haven't specified your model to have the constraint that nobody is in the 1 1 2 cell.
Julia Lee posted on Sunday, June 24, 2012 - 11:29 pm
Hi Dr. Bengt Muthen,
My question is regarding the LTA mover-stayer output on LATENT TRANSITION PROBABILITIES BASED ON THE ESTIMATED MODEL.
I am conducting a LTA mover-stayer with continuous variables. Is the output for the lower panel here for the movers only and hence the diagonal matrix refers to the stabiliity of the movers only (and not inclusive of the stayers' stability)? I am assuming measurement invariance. Stayers have zero probability of moving classes and movers have some probability of moving classes. I have different means for movers and stayers.
C Classes (Rows) by C1 Classes (Columns) .........1.........2 1 .......0.690...0.310 2 .......0.278...0.722 C1 Classes (Rows) by C2 Classes (Columns) .........1.........2 1....... 0.845...0.155 2....... 0.000...1.000
Hi, I was wondering whether the LTA parameterization 2 outlined in webnote 13 is equivalent to the model in Proc LTA (SAS), where x is includes as a covariate for both time 1 status and the transition probabilties?
Yes, it looks like the Mplus parameterization 2 of Web Note 13 is the same as used in Proc LTA.
Jane Smith posted on Wednesday, March 05, 2014 - 1:45 pm
I've run an LTA with a second order effect, an interaction and a covariate, and am trying to interpret the transitions. Specifically, how are the transitions under 'LATENT TRANSITION PROBABILITIES BASED ON THE ESTIMATED MODEL' different than those given by the LTA calculator--which I know are based on the levels of the covariates. In other words, how are the covariates/interaction allowed to influence the estimated model transitions? I've read webnote 13, but am unable to resolve my question.
I recently started using LTA and have some questions regarding this technique. I have measured subjects at two time points but made a classification with LCA at Time 1. Is it possible to use the classification at time 1 to re-score the subjects with the same variable at Time 2 and export that new classification to see if the subjects have changed classification between the two time points ? If yes, do you perhaps have an example how to do this?
I don't understand what you are suggesting. How is it different from doing LCA at each time point and comparing the classifications? Perhaps you are thinking of holding the measurement parameters of time 2 equal to time 1.
Thanks for your quick reply, I prefer not to perform a LCA for each time point because I want to maintain the same classes. Indeed I would like to hold on to the measurement parameters of time 1 and apply them to time 2. More specifically, I would like to maintain the orginal classes and see which of my participants moved between the classes at time 2.
You can fix all the time 2 parameters at the estimated values for time 1 so that there are no parameters to be estimated for time 2. That will give you a time 2 classification which can be different than at time 1 due to different time 2 outcomes.
Thank you so much for your help. I have been searching the Web for some examples, but havent come across similar approaches. Do you perhaps have a syntax I could build on? This would be very helpful because first of all, I am not sure where to find the parameters in my LCA output of time 1 and second, how to fix the parameters for LCA at time 2 for each class?
Use the SVALUES output option which gives you the final estimates. You will see which estimates go with time 1. Then change * (free) to @ (fixed) globally when copying this to the Mplus input for running time 2.