Jan Ivanouw posted on Thursday, August 19, 2010 - 10:46 am
I am working with a model for at psychological test with categorical indicators (items) trying to understand factor score calculation when there are no covariates (x)
Reading the Appendix 11, I find in expression 230 (for continuous y) both a representation of yi and of xi. In expression 229, though, there are only an representation of xi, and no representation of yi. There are the thresholds to sort of represent the y-score, but they does not vary across individuals, so it seems impossible to calculate the factor scores for individuals. I apparently have misunderstood something, but what?
Factor scores for categorical indicators cannot be calculated by hand. The procedure is iterative.
Jan Ivanouw posted on Thursday, August 19, 2010 - 10:59 pm
Hi Linda, Oh, I should have mentioned that I am building a simulation model (in Splus), så iteration is no problem.
It is important for me to be able to compare the factor scores I am producing in my program with the factor scores produced when using Mplus with the same data, and hence my problem:
I am using the expressions in the Technical appendix 11 to build into my program, but it seems that there might be an error in expression 229. To me there seems to be only parameters that vary over indicators, while the individual is only represented by eta, which is the variable the size of which for the individual is going to be determined using the iterative procedure.
Formula 229 is correct. Subscript i should be only on Eta. Parameters do not vary over individuals.
Jan Ivanouw posted on Thursday, September 09, 2010 - 2:46 am
I also thought I was wrong, but what I don't understand is:
The point is to find the value of eta (iteratively) that makes the observed score vector of the person most likely. To do this, the score vector must be included in the process somehow. Can you help me understand how the (categorical) score vector is used in the estimation of eta?