Anonymous posted on Friday, September 05, 2003 - 11:28 am
I am new to latent class analysis and I'm trying to running a 2 class model with 1 dichotomous and 3 3-category variables. I'm not sure how to specify the starting values for the thresholds. I tried putting in some numbers ranging from -2 to 2. However, I keep getting an error message that says: "IN THE OPTIMIZATION, ONE OR MORE LOGIT THRESHOLDS APPROACHED AND WERE SET AT THE EXTREME VALUES. EXTREME VALUES ARE -15.000 AND 15.000." I've tried putting in different values, but have not been able to fix the problem.
I'd appreciate any suggestions about what might be the source of the problem and how to fix it.
We tried to change the reference class in a latent class analysis by entering starting values for the thresholds, but the reference class did not change. Even when we tried using extreme starting values the reference class did not change. We only succeeded by constraining the thresholds with the @ symbol. Do you know why this might have happened?
in reference to my enquiry above your answer (March 04)
Y2$1 15.000 0.000 999.000 999.000
could you provide a little more clarity on what you said:
"...It is useful to know that membership in a certain class determines the distal outcome category".
My classes were mental health and distal outcome is suicide. So, are you saying, there were suicide attempts in class 1 but no attempts in the other classes and this is a function of class endorsement?
If Y2 is a binary distal, the Y2$1 15.000 result for a certain class implies that when a person is in this class there is zero probability of being in the highest category of the distal. The fact that the probability is zero and not for instance 0.25 (greater than zero, not ignorable, but not close to 1 or even 0.5) makes the relationship between the latent class and the distal stronger.