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Utilities for single-concept conjoint w/ allocation

I need guidance on how to correctly calculate the utilities for the below conjoint exercise that was fielded outside Sawtooth.
A full profile conjoint with a single-concept per task (design was built as CBC w/ 1 concept and None option): a user is asked to allocate 100% between a fixed set of existing products and a potential product X.
Now before I upload the collected data to Sawtooth how should I treat the allocated %s for those fixed products to ensure the utilities are correctly estimated? Just add them to None option, i.e. 100% minus product x allocation? Thanks!
asked Oct 13, 2017 by kasharaz (140 points)
retagged Oct 13, 2017 by Walter Williams

1 Answer

0 votes
That would be the easiest way, as long as you don't care about the shares of any of the particular fixed products.  If you DO care about the shares of those individual fixed products then you'll want to recode your design to reflect one Product X with a new brand variable (Brand level X) varying attributes and levels plus several fixed brands (no varying attributes and levels, but levels of the new brand attribute).  

You could also think about this as an alternative specific design where all the alternatives have levels of the brand variable, but Product X has some alternative- specific attributes as well.
answered Oct 14, 2017 by Keith Chrzan Platinum Sawtooth Software, Inc. (66,225 points)
Thanks Keith for your helpful answer! In fact, I will also need the shares of fixed products for this one. My follow up question - in a recoded design with the new Brand attribute added should I set '0's to all current varying attributes when I have a fixed product (as with alternative-specific design) or add 'NA' level to each varying attribute and set NA?
Treat it as if it were alternative specific and you should be OK
Thanks for your prompt confirmation and guidance