I am trying to calculate utilities for a ACBC conjoint.
It has 4 levels plus price. Each of the levels has a 'not included' option (at £0.00), and I want to constrain the utilities so that 'not-included' has a lower utility than the other levels.
I am running piecewise price utility with 5 levels, constrained negative.
When i try to calculate utilities without constraints, it takes a fair few iterations to calculate but eventually converges quite neatly.
Running the utilities with constraints appears to be fine for 2 of my 5 user segments.
However, when I try to run 3 out of 5 of my user segments with the constraints, for the first few iterations it appears to work fine, but then all of the price level utilities (including at the top of the price range) suddenly jump up and end up after 5k iterations plus to be heavily positive- much more positive than the other attribute levels.
Obviously this shouldn't be the case, so I was wondering if anyone knows anything that might be causing it, or anything that I could do to prevent it.
Using v. 6.6.18