Have an idea?

Visit Sawtooth Software Feedback to share your ideas on how we can improve our products.

Add "Not offered" level to cbc

Hi all!
Thank you in advance.  I have completed a CBC study.  Now, we want to add a "not offered" level to three attributes.  I assume I just add that level and put zeros in for the utilities for each respondent.  
Is that correct?
Thank you.
asked Jun 19, 2019 by anonymous

1 Answer

0 votes
Not correct, sorry.  CBC utilities are scaled such that their average is zero.  So, adding a new level with a utility value of zero is to say that this new level has the average preference of the other levels.  If you didn't include a "not offered" level in the study to begin with, it's hard to know how to figure its utility.

I once was asked by a client to do this, many years ago, when we received a project that had forgotten to include the null (assumed worst utility) level.  We decided to impute a value per each respondent's HB score equal to the worst utility level for that attribute for that respondent, minus some small utility amount such as 0.1 or 0.5.  We warned the client of the assumptions we were making in that imputation.
answered Jun 19, 2019 by Bryan Orme Platinum Sawtooth Software, Inc. (176,815 points)
Attribute not mentioned in CBC