Calculate ACA Utilities

Before computing part-worth utilities, you must first have downloaded a data file (studyname_data.sqlite) from your Web server (or accumulated the data from PCs), and placed it within your study directory, where all other study-related files are resident. We use Ordinary Least Squares to compute part-worth utilities. The resulting part-worths are saved to a STUDYNAME.utl file, which is a text-only file with a specific format. (Please see Appendix A for more information on interpreting conjoint analysis results.)

Select Analysis | Calculate ACA Utilities using Ordinary Least Squares.... Choose Settings.... You are able to specify a number of options on this dialog:

Respondent Numbering Method

You can choose from five options for assigning respondent numbering. This lets you specify how the respondent numbers (case IDs) are to be generated. User Name is one of the passwords from the passwords module. You should only choose this if these values were purely numeric (no letters). Password is also one of the passwords from the passwords module. You should also only use this if the passwords were purely numeric (no letters). Internal Interview Numbers are those that the system assigns when respondents complete the survey over the Web. There can be gaps in the sequence if some respondents started a survey but didn't finish. Sequentially Assigned Numbers (default) are integers 1 through n. Other lets you choose another numeric variable to use for respondent numbering. This last option is useful if you are linking surveys from another source and need to merge the data sets by a "passed-in" variable.

Respondents to Include

All Respondents: Choose this option to export all respondents: both complete and incomplete. Data for questions that were not completed are left blank.

Qualified/Completes Only: Choose this option to export only qualified complete data records. A survey is considered qualified complete when respondents click the Submit (Next) button on a terminating question that is marked with a qualified status.

Disqualified and Incompletes Only: Choose this option to export only disqualified and incomplete data records. A survey is considered disqualified when respondents click the Submit (Next) button on a terminating question that is marked with a disqualified status. A survey is considered incomplete if respondents have not reached a terminating question.

Prepare for Utility Computation...

Click Prepare for Utility Computation... to compute utilities and save the STUDYNAME.utl file to the current folder. A report appears summarizing the results of the computation, and (on a separate tab) listing the respondent utilities one respondent record per row. You can save the results to an Excel file by clicking Save As....

---

Output

When OLS estimation is completed, the output is displayed in a report window. The first (Summary) tab displays the average part-worth utilities across respondents (normalized by the zero-centered diffs method), and the average attribute importances. On the second (Individual Utilities) tab are the raw utility data for each respondent, organized as one row per respondent. Click the Save As... button to save the data as an Excel (.XLS) file.
Zero-Centered Diffs Method: The Summary tab displays the average rescaled utilities (as well as the standard deviations) under the zero-centered "diffs" method. The diffs method rescales utilities so that for each individual the total sum of the utility differences between the worst and best levels of each attribute across attributes is equal to the number of attributes times 100. This normalizes the data so that each respondent has equal impact when computing the population average.

A studyname ACA.utl file is also automatically generated, which is a text-only file with a specific format. This file may be directly imported into the SMRT program for market simulations.