I'm running an ACE with moderator script, on Mx. When I drop one of the parameters (U), I receive this message-

Mx starting optimization; number of parameters = 7

*** WARNING! ***

I am not sure I have found a solution that satisfies

Kuhn-Tucker conditions for a minimum.

NAG's IFAIL parameter is 6

Looks like I got stuck here. Check the following:

1. The model is correctly specified

2. Starting values are good

3. You are not already at the solution

The error can arise if the Hessian is ill-conditioned

You can try resetting it to an identity matrix and fit

from the solution by putting TH=-n on the OU line

where n is the number of refits that you want to do

If all else fails try putting NAG=30 on the OU line

and examine the file NAGDUMP.OUT and the NAG manual

I'm not sure what the OU line refers to.. any ideas?

The rest of the output works, except for the probability, which says its incalculable.

Thanks!

There exist scripts to run such analyses in the open source and actively supported OpenMx. Please stop using classic Mx; it is no longer supported.

You can put the options in an Option line before the End statement. I suspect that you are using ordinal data and that the solution is ok, but at least check with different starting values whether you get the same fit and parameter estimates. MxTryHard is the way to go with OpenMx.