This QScript computes Sawtooth-style preference shares for the alternatives in a MaxDiff experiment using individual-level parameter means. The formula is given below.
Example
This example uses the data from the MaxDiff Case Study. The table on the left shows a SUMMARY of Individual-Level Parameter Means generated using Q's Segments tool. The table on the right shows a SUMMARY of the preference shares generated by this QScript. In this example there were 5 alternatives shown in each task, so a value of 5 was entered when the QScript was run.
Technical details
Input data
This QScript uses data from individual-level parameter means from a MaxDiff experiment. The variables should be combined into a Number - Multi question that has the string Individual-Level Parameter Means in the name. The individual-level parameters question can be generated in Q from a segmentation of a ranking question (by right-clicking a node of the tree and selecting Save Individual-Level Parameter Means and Standard Deviations).
Alternatively, the individual-level parameter means can be computed externally and imported into Q as part of a larger data set. In this case:
- The variables should be combined as a Number - Multi question.
- The text Individual-Level Parameter Means should be included in the question name.
Outputs
A new Number - Multi question is generated in the project, and a table is added to the report to show the average of the computed values.
Further reading: MaxDiff software
Each respondent's utilities are first zero-centered by subtracting the average. The zero-centered utility score for alternative \(j\) is denoted \(u_j\). The un-scaled Sawtooth-style preference parameter for alternative \(j\) is then:
\[P_j = \frac{e^{u_1}}{e^{u_1} + K - 1}\]
where \(K\) is the number of alternatives that were shown to the respondent in each task of the MaxDiff experiment.
The final Sawtooth-style preference share is obtained by scaling these parameters so that they add up to 1 (or 100%):
\[S_j = \frac{P_j}{\sum_jP_j}\]
How to apply this QScript
- Start typing the name of the QScript into the Search features and data box in the top right of the Q window.
- Click on the QScript when it appears in the QScripts and Rules section of the search results.
OR
- Select Automate > Browse Online Library.
- Select this QScript from the list.
Customizing the QScript
This QScript is written in JavaScript and can be customized by copying and modifying the JavaScript.
Customizing QScripts in Q4.11 and more recent versions
- Start typing the name of the QScript into the Search features and data box in the top right of the Q window.
- Hover your mouse over the QScript when it appears in the QScripts and Rules section of the search results.
- Press Edit a Copy (bottom-left corner of the preview).
- Modify the JavaScript (see QScripts for more detail on this).
- Either:
- Run the QScript, by pressing the blue triangle button.
- Save the QScript and run it at a later time, using Automate > Run QScript (Macro) from File.
Customizing QScripts in older versions
Next
- QScript for more general information about QScripts.
- QScript Examples Library for other examples.
- Online JavaScript Libraries for the libraries of functions that can be used when writing QScripts.
- QScript Reference for information about how QScript can manipulate the different elements of a project.
- JavaScript for information about the JavaScript programming language.
- Table JavaScript and Plot JavaScript for tools for using JavaScript to modify the appearance of tables and charts.