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Fixed price in cbc vs. utilities

Dear All,
I have prepared a CBC design with below attributes:

Brand : 13 levels
Price : 17 levels

There is brand A with 3 price levels (1-3) ,Brands B,C,D,E with 6 price levels (4-9) and 8 brands F,G,H,I,J,K,L,M each of these brand have own fixed price. Respectively price level 10,11,12,13,14,15,16,17, where brand F appears only with price 10, brand G with price 11 etc.

It required some manual work with the design file to avoid prohibitions but my question regards analysis.

After collecting the data Im going to recode attribute Price onto 3 price attributes:
Price1 for Brand A
Price2 for Brands B,C,D,E
Price3 for rest of brands with fixed prices.

and estimate utilities by HB.
I think that utilities for the attribute Price3 can be ignored for shares of preference as whole information about products F - M are already captured by brands utililies since each brand was always shown with just 1 price. So when recoding .cho file I could assign to Price3 just zero.

Is it justified to ignore utilities for Price3?

asked Nov 9, 2017 by robson Bronze (750 points)

1 Answer

+1 vote
Best answer
There are various ways to either use alternative-specific designs or to trick the software by manually manipulating the design (it sounds like you did the latter).

When you go to analyze the data for analysis, you should make sure it is formulated as an alternative-specific design, where you have:

Attribute 1, Brand: 13 levels
Attribute 2, Price for A: 3 levels
Attribute 3, Price for B-E:  6 levels

Attribute 2 only is applicable for Brand = A
Attribute 3 only is applicable for Brands = B through E

No price attribute is coded for brands F-M.  The total utility of the brand plus the fixed price part is captured in the brand utility (within attribute 1).
answered Nov 9, 2017 by Bryan Orme Platinum Sawtooth Software, Inc. (169,815 points)
selected Nov 10, 2017 by robson
Thank you Bryan. Very important note .