Displaying 3 results from an estimated 3 matches for "underidentification".
2013 Feb 09
1
Troubleshooting underidentification issues in structural equation modelling (SEM)
...move them from the parameters to estimate making it a
total of *180 parameters to estimate*.
- My degrees of freedom is therefore 2346 - 180 = 2166, making it an
over identified model by the t-rule.
Questions
1. Is the low variance of some of my items a possible cause for the
underidentification? I was advised previously to remove items with zero
variance which led me to think about items which are very close to zero.
Should they be removed too?
2. After reading much, I think but am not sure that it might be a case
of empirical underidentification. Is there a systematic way of...
2012 Jan 17
2
bayesian mixed logit
Dear all,
I am writing an R code to fit a Bayesian mixed logit (BML) via MCMC / MH algorithms following Train (2009, ch. 12).
Unfortunately, after many draws the covariance matrix of the correlated random parameters tend to become a matrix with almost perfect correlation, so I think there is a bug in the code I wrote but I do not seem to be able to find it.. dull I know.
Has anybody written a
2010 Jun 04
1
sem R: singular and Could not compute QR decomposition of Hessian
Can somebody help me with the following issue (SEM in R), please:
When I run the model (includes second order models) in R, it gives me the following:
1) In sem.default(ram = ram, S = S, N = N, param.names = pars, var.names = vars, :
Could not compute QR decomposition of Hessian.
Optimization probably did not converge.
2) I have aliased parameters and NaNS
or sometimes when