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how to interpret "None" option in ACBC/HB Report Summary Results

it would be great if somebody could help me understand the 3 following points related to the variable 'none' being reported in Excel Report Summary Results as well as the table of estimated values per level x attribute.
Q1: to what does this variable 'none' refer to ?
 it seems that an additional utility value is calculated for this variable "none" (header title),  even though this variable is not part of the attributes being tested.
Q2: does it refer to some kind of constant that need to be estimated as well along with utilities per level x attribute.

Q3: in case one is interested in estimating the total utilities associated to a specific combination of levels across attributes, how to deal with this 'none' ?  Is it recommended to ignore it ?

Many thanks in advance for your help
asked Sep 6, 2016 by Rem (200 points)

1 Answer

0 votes
The None utility in ACBC comes from the "Screener" section in the interview, where respondents indicate that each concept is "a possibility" or "not a possibility".  The "not a possibility" alternative (as if it were a binary choice in a choice design) is the "none" alternative in ACBC and it receives a weight.  You may just ignore it if you would like.  But, it is required in the model setup to better estimate the utilities for the attributes and levels in your attribute list.
answered Sep 6, 2016 by Bryan Orme Platinum Sawtooth Software, Inc. (176,815 points)
Dear Bryan,
thank you very much for your swift reply and support.
How is the None utility in ACBC interpreted during simulation?