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Equating transitional probabilities |
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I run LTA analysis on 4 waves of survey data. I use 9 3-level variables and specify model with 6 classes. I constrained item-response probs and test invariance of transitional probabilities between the waves. Here is my code. !Time 1 to Time 2 C2#1 on C1#1 (1001); ...... c2#5 on C1#6 (5006); ! Time 2 to Time 3 c3#1 on c2#1 (1001); ------- c3#5 on c2#6 (5006); !Time 4 to Time 3 c4#1 on c3#1 (1001); ---- c4#5 on c3#6 (5006); With this model I estimate 153 parameters.However, examples that I found on the web (see https://www.statmodel.com/download/LTA_DP_FINAL.pdf) call for additional constrain [C2#1] (11111); ..... [C2#5] (55555); [C3#1] (11111); ..... [C3#5] (55555); [C4#1] (11111); ...... [C4#5] (55555); It doesn't seem right unless unless I'd like to constrain prevalence of LC. Can you please clarify this. |
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Have a look at Chapter 14 of the UG, pages 558-559. The table on page 559 shows that both a and b contribute to the logits in the cells and therefore the transition probabilities. The a's don't correspond to the prevalence of the LC, but are intercepts. |
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Dear Dr.Muthen, Thank you for pointing out the differences in parametrization. After Reading Chapter 14 it's clear to me. |
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