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Which "None" Weight should I choose in SMRT Scenario Specification for a CBC/HB?

I conducted a CBC analysis and would like to check its validity with the help of my two holdout-tasks.
Therefore, I used Sawtooth SMRT Market Simulator to estimate the Share of Preferences and the Rnd. First Choice for the concepts within my holdout task, which includes a non-option.
I found that I can include a none-option in the market simulation by changing the value of the "none" Weight in Advanced Setting. I unfortunatly do not know which value I should insert. How do I determine the right value?
I got 2 products and 1 none-option per choice task and overall 12 tasks.
Thank you very much for your help,
asked Jan 28, 2014 by anonymous

1 Answer

0 votes
If your simulated choice scenarios essentially match the same number of concepts + None for your experimental tasks (that captured the data for estimating utilities), then you really shouldn't have to change that value different from 1.0 to get appropriate estimates of what new respondents would pick in those new choice scenarios.

So, to turn None "off" you set it to 0.  To turn it "on" with its default weight you set it to 1.

Another issue is that respondents tend to understate their None likelihood in market research surveys (they typically tend to exaggerate purchase likelihood).  If you have external data indicating some direction regarding what the None rate should be, then you might think about adjusting the None weight to something like 1.5, 2, or 3, etc.
answered Jan 28, 2014 by Bryan Orme Platinum Sawtooth Software, Inc. (140,065 points)
Thank you very much!