Conjoint studies frequently include product attributes for which almost everyone would be expected to prefer one level to another. However, estimated part-worths sometimes turn out not to have those expected orders. This can be a problem, since part-worths with the wrong slopes, or coefficients with the wrong signs, are likely to yield nonsense results and can undermine users' confidence.
New Features in CBC/HB v1.5 Upgrade
- Utility constraints
- Saving "draws" files optional
- Part-worth estimates history
Version 1.5 of CBC/HB provides the capability of enforcing constraints on orders of part-worths within attributes, and on signs of linear coefficients. The same constraints are applied for all respondents, so constraints should only be used for attributes that have unambiguous a-priori preference orders, such as quality, speed, price, etc.
Evidence to date suggests that constraints can be useful when the researcher is primarily interested in the prediction of individual choices, as measured by hit rates for holdout choice tasks. However, constraints appear to be less useful, and indeed can be harmful, if the researcher is primarily interested in making aggregate predictions, such as predictions of shares of choices. For more information about applying constraints in HB analysis of choice data, please see Rich Johnson's article entitled, "Monotonicity Constraints in Choice-Based Conjoint with Hierarchical Bayes" at www.sawtoothsoftware.com in the Technical Papers library.
The first version of CBC/HB used up a great deal of computing resources, especially in terms of hard drive space, because of the "draws" file. Draws files can easily grow to a Gig or more in size. We expect that most CBC/HB users are probably not interested in the "draws" file, but instead focus their attention on the average point estimates of the part-worths for each respondent. With Version 1.5, the user can specify that a "draws" file is not needed.
Some users have wanted to plot the successive estimates of part-worths after every kth iteration. CBC/HB v1.5 saves a history of the part worths to a flat file, which can be easily imported into the charting software package of your choice.
The upgrade fee for CBC/HB v1.5 is $400 for v1.0 users. Please call us at 360/681-2300 for more information or to order.