There are several possible reasons for the estimation iterations not to stop:

 

(1) Your judging design is very sparse.

 

(2) The analysis is over-constrained (too many facets are anchored or centered)

 

(3) The analysis is under-constrained (too few facets are anchored or centered)

 

(4) You have nested facets.

 

In general, every facet except one needs to be anchored or centered, so that Noncenter= specifies one, unanchored facet.

 

If any facet is nested within another facet, e.g., there is a "student" facet and also a "student gender" (sex) facet, then nesting needs to be resolved by anchoring or group anchoring.

 

If the changes per iteration are very small or are oscillating up and down about equally, then the estimates are as good as they can be. Press Ctrl+F to stop iteration and move on to fit computation.

 

You can also use the Estimation menu to make the changes per iteration smaller, or to change the estimation method.