I´d be very grateful for a clarification about the estimation of the None Utility within ACBC designs and HB estimation.

In the ACBC´s technical guide it says:

"Each respondent has marked T concepts as "possibility" or "not a possibility." We treat these each as binary choices, where the respondent is assumed to compare the utility of the concept to the utility of a constant threshold prior to making a choice. The constant threshold is included in the design matrix as an additional dummy coded column."

I don´t get the last bit.

Is the none utility part of the iterative estimation procedure (MCMC) drawing on the choice tournament data or fixed after the screening section?

Does "design matrix" refer to the variance-covariance matrix D respectively is the none utility one element of the vector β (part worth utilities) or is it something completely different?

Thank you very much for your support!

Best,

Chris