Re: st: odd behavior of -sem- in Stata 13

[jpitblado@stata.com (Jeff Pitblado, StataCorp LP)]

Lance Erickson <lance_erickson@byu.edu> is using -sem- in Stata 13 and gets an
error message where -sem- in Stata 12 just fits the model:

> Has anyone experienced problems estimating SEM models in Stata 13 that ran
> without problems in Stata 12 (Windows 7)?
> 
> I had prepared some analyses that were successfully estimated by Stata 12
> and now going back to them after installing Stata 13 there are some
> problems. Here's the code... 
> 
> ********
> sem (tenure skdis5r dauthority managersup satcowr satjobr <- WRKCNTXT) ///
> 	(meaningful <- WRKCNTXT) ///
> 	(perform <- marital WRKCNTXT meaningful) 
> 	if creative==1, ///
> 		covstr(e.satcowr e.satjobr, unstructured) ///
> 		covstr(e.satcowr e.managersupp, unstructured) ///
> 		covstr(e.dauthority e.satjobr, unstructured) ///
> 	method(mlmv)
> ********
> 
> And here is the error I get ...
> 
> ********
> note: The following observed variable name will be treated as a latent
> variable: ANsample.  If this is not your intention use the nocapslatent
> option, or identify the latent variable names in the latent() option.
> latent variable 'ANsample' not referenced in the model
> r(198);
> ********
> 
> The model does run in Stata 13 if I identify the latent variable in the
> -latent()- option as suggested by the error message. But, the SEM manual
> says that the command should identify variables as latent if the first
> letter is capitalized. Just to check, I did manage to access Stata 12 and
> run the exact same command runs fine without the -latent()- option. Could
> this be a feature change across the versions or is it a bug?
> 
> What seems particularly odd to me is that I was able to get Stata 13 to
> estimate the models by deleting any variables from the data set that weren't
> included in the model. I didn't need to add the -latent()- option either.
> I'm deleting many variables when I do this and I haven't taken the time to
> explore whether it's a single variable or set of variables that need to be
> deleted.
> 
> Again, does anyone know if there are known bugs with -sem- in Stata 13 that
> might account for this? Or am I ignorant to some new feature?

Lance has found a bug in some new latent variable parsing logic that was added
to -sem- in Stata 13.  There is a variable in the dataset with a capitalized
name that -sem- is not handling correctly.

We have reproduced the problem and have a fix that will be available in a
future update to Stata 13.

In the mean-time, Lance has discovered the two work-arounds to this problem.

--Jeff
jpitblado@stata.com
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