ACA Calibration Questions (Question Text Tab)
(Optional Questions)
The computer composes a series of "calibration concepts" using those attributes determined to be most important. These concepts are chosen to occupy the entire range from very unattractive to very attractive for the respondent. The respondent is asked a "likelihood of buying" question about each.
According to the number of calibration concepts questions (n) you specified to include under Specify ACA Interview Parameters screen, n calibration concepts are included in your questionnaire.
The calibration concepts can be displayed in "vertical" mode as separate questions (one on top of the other, on a single or across multiple pages) or in "horizontal" mode as a unified series of concepts arranged horizontally on a single page.
We first present the concept we expect the respondent to like least among all possible concepts, and the second is the one we expect to be liked best. Those two concepts establish a frame of reference. The remaining concepts are selected to have intermediate levels of attractiveness.
This information can be used to calibrate the part-worth utilities obtained in the earlier part of the interview for use in Purchase Likelihood simulations during analysis. Conjoint part-worths are normally determined only to within an arbitrary linear transformation; one can add any constant to all the values for any attribute and multiply all part-worths by any positive constant. The purpose of this section is to scale the part-worths non-arbitrarily, so that sums of part-worths for these concepts are approximately equal to logit transforms of the respondent's likelihood percentages.
The horizontal screen format is:
When using the horizontal format, the Calibration Concept questions must be displayed on the same page. If you choose the vertical format (one concept on top of the other), you can format them on a single or across multiple pages. You define those formats on the Question Format tab in the Question Layout field.
If you plan only to conduct share of preference simulations, and particularly if you are using the ACA/HB system for hierarchical Bayes estimation, you may consider not including calibration concepts in your ACA survey. See Estimating ACA Utilities for more information on the use of calibration concepts.
