The plots I get from doing this are different from the plots I get from when I plot the data from the section labeled,
RESULTS IN PROBABILITY SCALE
SAL1 Category 1 0.588 Category 2 0.412
Obviously I am confused as I had expected these would be the same.
My questions are, 1. Which is correct! 2. What am I plotting (if anything) when I calculate what I thought were prob using just a logistic regression approach? 3. What am I plotting when I plot the data from the “Results in Probability Scale” section? 4. Finally a basic question - Am I predicting the 1 in data or Category 1 as indicated in Mplus?
If your growth model has growth factors (random effects) with non-zero variances the outcome probabilities have to be computed via numerical integration over the distribution of the random effects. This is what is done in the Probability output and in the graphics of Mplus. It is hard to do by hand.
What you are computing is the outcome probabilities at the means of the growth factors. The two approaches are not the same with a non-linear model such as this.
Mplus creates categorical variable scales labeled 0, 1, ... Therefore category 1 in Mplus is 0 and category 2 is 1. With a binary outcome Mplus models the probability of category 2 as usual in logistic regression.