Calculating results in probability scale
Message/Author
 Anonymous posted on Tuesday, July 24, 2012 - 9:01 am
I am looking for a guide as to how Mplus calculates 'results in probability scale' having estimated the latent class model. Can you advise?
 Linda K. Muthen posted on Tuesday, July 24, 2012 - 10:53 am
The formula is

p = 1 / (1 + exp(threshold))
 Anonymous posted on Tuesday, July 24, 2012 - 11:41 am
Thank you. And how are the class membership probabilities calculated?
 Bengt O. Muthen posted on Tuesday, July 24, 2012 - 12:00 pm
Mplus prints estimates of [c#1 c#2...]; that is the logits corresponding to the intercepts/means of the multinomial regression on covariates (no covs implies that the intercepts are the means). Then use UG Chapter 14 formulas on pages 441-445 to translate from those logits to probabilities.
 Peter Halpin posted on Sunday, May 03, 2015 - 5:59 pm
To follow up on this question, how does Mplus obtain the SEs for the results in probability scale, following an LCA? As short explanation or reference would be great, thank you.
 Peter Halpin posted on Sunday, May 03, 2015 - 7:40 pm
Sorry I should have looked into this more closely before posting. It seems that the SEs for the results in probability scale can be obtained using the delta method and the output in TECH3. Thanks, Peter
 Bengt O. Muthen posted on Monday, May 04, 2015 - 7:49 am
Right.
 Virginia Rangel posted on Wednesday, February 27, 2019 - 8:45 am
I am running a three-step LPA using syntax that I have successfully used before and the output is not giving me the results in probability scale. I have checked that I have not made any mistakes in the syntax, and it's the same just with different variable names. I've tried running the LPA using BCH, R3STEP, and DE3STEP, and nothing is giving me the full output with the results in the probability scale. I can send my syntax but unfortunately cannot send my data as they're federally restricted data and my license prohibits that.
 Bengt O. Muthen posted on Wednesday, February 27, 2019 - 11:27 am
BCH and DE3STEP are for continuous distal outcomes. See Tables 6 and 7 of Mplus Web Note 21. Use DCAT.
 Virginia Rangel posted on Wednesday, February 27, 2019 - 12:05 pm
Thanks for the quick response. My outcomes are continuous (high school GPA and number of courses), so BCH should be OK. I re-ran and still am not getting the results in probability scale. I'm sort of at a loss for what I'm doing differently and wrong.

A colleague recommended (and I've been reading about) the manual 3-step approach. Might that be an appropriate solution here?
 Bengt O. Muthen posted on Wednesday, February 27, 2019 - 1:05 pm
You can send your output to Support along with your license number. Also, try the manual approach described in web note 21.
 Bengt O. Muthen posted on Wednesday, February 27, 2019 - 1:07 pm
Note that probability output would be relevant only for a categorical outcome not a continuous one.
 Virginia Rangel posted on Wednesday, February 27, 2019 - 1:19 pm
Thanks, I will look at the note and keep working. Where do I find comparable output to help me interpret the nature of the classes? (Sorry, I'm used to working with LCA, this is my first time with LPA...)