Ngene in SurveyEngine: Common parameter, different levels

[DrWho]

Dear Michiel and Ngene Team,

As stated in my previous post, I would like to have one common price parameter in my model, but different levels for each alternative:
viewtopic.php?f=4&t=1193

Unfortunately, Ngene on SurveyEngine does not allow this configuration. I can either specify a common attribute with the same levels or alternative specific attributes.
The SurveyEngine support team is also unsure how this could be solved.

How much efficiency will I lose when I specify Ngene with alternative specific attributes but then estimate a single parameter in the final mixed-logit model?
Do you have an alternative in mind how I can solve this?

[Michiel Bliemer]

I suspect that efficiency loss is not that great if you optimise for alternative-specific parameters but estimate the model using a generic parameter.

One alternative is to use the full desktop version of Ngene in which you can change the script yourself.

An alternative in SurveyEngine is to specify a single attribute with all price levels combined and then impose constraints on which level can appear in what alternative using constraints.

Michiel

[DrWho]

Thank you very much!