Does opt-out Alternative count for likelihood calculation?

Question

So if you present 2 alternatives and an opt-out option how do you calculate the likelihood for that?
Greetings

Answer 1

Yes, it does.

Your null likelihood for a case with two alternatives plus an opt out is 0.3333333.  

If your utilities for Option A is 1 and for option B is 0 and for the opt-out is 0 then their exponentiated utilities are, respectively, 2.718, 1 and 1 and their choice probabilities are 0.576, 0.212 and 0.212.  If the respondent chooses the first alternative, then your observed likelihood is 0.576.

Comments

Thanks a lot!