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CBC logit coefficient value affected by prohibition


I am running an analysis for a dual response CBC data with only 2 choices per set and one prohibition among the 31 levels included (5 in 5 dimensions and 6 in 1 dimension). I included an interaction between the dimensions that contained these 2 levels as proven to be significant by the interaction search. (Can this be the source of the problem??)

The estimation of the 2 prohibited levels is somewhat problematic.

In the lighthouse program:
1- one level had an unrealistic estimation with a negative sign (expected to be positive and better than the one next to it).
2- both of them did not report any standard errors nor t-ration

In the stand-alone Latent Class analysis (1 group) : (results are disutilities as the signs are flipped)
1- disutility signs are all ok for one level but not for the other (opposite situation from the above case)
2- Standard Error is reported 0 for all 31 levels
3- t-ratios are a huge number (6 or more digit number)

I get a warning in both cases that says:
"The data is ill-conditioned. A ridge adjustment was made."  

How can I solve all these issues? Thanks for your help.
asked May 7, 2020 by AMYN Bronze (3,000 points)
edited May 7, 2020 by AMYN

1 Answer

+1 vote
Best answer
If you add a prohibition that involves two attributes, you have rendered them no longer independent, as is assumed by the way we code interactions.  You should not estimate interactions in this way.
answered May 7, 2020 by Keith Chrzan Platinum Sawtooth Software, Inc. (105,750 points)
selected May 8, 2020 by AMYN