In this article
You can use the Discrete Choice Model (DCM) Conjoint Element to assist you in creating a coherent set of questions for conjoint analysis.
Note: To use the DCM element, ask your Forsta account representative to enable the DCM element.
1: Adding a Discrete Choice Model
To add a Discrete Choice Model element, first select the + Element button to add a new survey element. Then select Rate, Rank, and Sort under Question Types and select Discrete Choice Model. Then select Add.
While viewing the newly added question element in the staging area, select the more options (...) drop-down menu and select Update Styling. The Style Editor modal displays.
The columns represent concept choices, from which participants select their most preferred option. You can change the number of concepts (columns) displayed to participants at any one time from two to at most twelve.
From the Style Editor, you add the required design file in one of two ways:
1.1: Generating New Design File
To generate a new design file, select Generate New Design File under File Information in the Style Editor.
Fill out the required fields before you Save and generate a design:
Number of Respondents (required): The number of participants who will see this question. This is the number of unique combinations of tasks and attributes. It must equal or exceed the number of unique sets of choice sets.
Tasks (required): The number of levels (questions) to be used. This will be the number of questions the participant sees.
Attributes (required): The number of attributes to be used. The count will dynamically update to reflect the attributes added.
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Legend: Select this option to show a legend to participants. The legend will be an added column to the left of the concepts, and will have one row per attribute. Add the legend text using the text input fields.
Legend Top Text: The text to label the top of the legend column.
Legend Row Text: The text to label the bottom of the legend column, in the answer row.
Next, scroll down in the Style Editor to the Attributes header.
Add the attributes by selecting Add Attribute.
Add Legend Text for each attribute. The legend text is displayed on the left side legend. Use the + button to add more attributes. Use the x button to remove attributes.
Then, select the attribute to open the drop-down and select Add Level to add levels to each attribute.
The levels will be randomly combined across attributes to generate your design file. Use the + button to add more levels. Use the x button to remove levels.
Texts for attributes and levels can be added and changed at any time. At least two attributes with at least two levels each must be added before generating the design. Select Generate Design to generate the design file. The status of the design file creation is noted under DesignStatus.
Tip: The numbers entered for Number of Respondents, Tasks and Attributes will affect the design file generation time, as will the count of columns (concepts). Higher counts for any of these will increase the time to completion.
You may close the Style Editor modal while waiting for the file to finish generating. The design status will update each time the Style Editor modal is opened. The design status will not update if the Style Editor modal is already open.
Select Save to complete set up. Next, test the survey to review your newly created Discrete Choice Model element.
1.2: Uploading Existing Design File
If you choose to provide your own DCM design file, prepare the file before uploading.
Tip: You can export a design file generated via the DCM Style Editor using System Files. Since this file was generated by Decipher, it does not require extra preparation before being uploaded.
The first step is to extract the raw design like the one shown above into a tab-delimited text file. Save the design file in the tab-delimited format. Both tab-delimted .txt design files and .dat design files can be uploaded.
The design file is now ready to upload. Drag it into the modal or select it by browsing through your computer's file system.
Once the design file has been uploaded, the following fields will automatically populate based on the design file:
Number of Respondents
Tasks
Attributes.
Uploading a design file will automatically generate the correct number of attributes in the Style Editor. Each attribute will have two levels (the minimum required per attribute). None of the texts for the levels or attributes will automatically populate, unless matching texts have already been saved for that DCM question.
If any attributes in your design file have more than two levels, use Add Level to add the appropriate number of levels to those attributes. The level is the number from the column for that particular row attribute.
After the attribute and levels have been set up, select Save.
Finally, test out the DCM to ensure it is set up as desired.
2: DCM Best Practices
Below are best practices for building a conjoint with Decipher's DCM conjoint element.
Standard Question Text
Please choose the option you would choose if these were the only options available.
For DCM Design:
Minimum Sample Size
n = 300 respondents
Attributes
Minimum: 2
Maximum: 7
Levels per Attribute
- Minimum: 2
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Maximum: 6
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Recommendations for Price Attribute:
Maximum of 5 levels
Keep price levels simple and distinct
Avoid overlap with value-related attributes (that is, do not include both "price" and "value" in the same study to preserve mutual exclusivity of concepts)
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Number of Random Tasks per Respondent
Minimum: 6
Maximum: 12
Number of Concepts per Random Task
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Durables (durable goods): 2 – 4 concepts
Durables are physical products with a long lifespan, typically purchased infrequently and used over time. These are high-involvement purchases, meaning consumers usually spend more time evaluating their options before buying.
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CPG (Consumer Packaged Goods): Up to 12 concepts.
CPGs are everyday products that consumers purchase frequently, use quickly, and typically have lower involvement in the purchase decision compared to durable goods.
Summary Table of Durable vs CPG based on best practices:
| Category | Durables | CPG / Non-Durables |
|---|---|---|
| Lifespan | Long-term | Short-term / Consumable |
| Purchase Frequency | Infrequent | Frequent |
| Decision Process | Deliberate, research-heavy | Fast, often habitual |
| Concepts per Task | 2-4 | Up to 12 |
| Common Examples | cars, appliances, furniture | snacks, drinks, toothpaste |
3: Adding CSS to DCM
You can add CSS to the conjoint element with our XML Style System.
Example:
<style name="respview.client.css"><![CDATA[
<style>
#question_q1 tr.dcm_even {
background-color: green !important;
}
#question_q1 tr.dcm_odd {
background-color: yellow !important;
}
tr.even .dcm_legend {
background-color: blue;
}
</style>
]]></style>Learn More: XML Style System
4: Design Metrics
Design metrics provide various ways to evaluate the quality of the design. Three files are generated and available for download in the "Shared Documents" section on the Project Overview page. Provided are counts, frequencies, and standard errors.
5: Limitations
Only random design method is supported. Other design methods, such as balanced, are not available.
None option is not supported.
Prohibitions are not supported.
Using a DCM inside a loop element is not supported.
DCM cannot be duplicated using the Survey Editor Duplicate action. You will need to manually add a new element.
Versions are assigned based on least-filled.
For manually uploaded design files, levels and attributes need to start with an index of
1.
6: Learn More
To use the XML Editor to create a DCM Conjoint Element, see Customizing the DCM Conjoint Element
For reports, see Reporting on the DCM Conjoint Element