How to Do the Statistical Analysis of Choice-Based Conjoint Data

This article describes how to create a choice-based conjoint model using discrete choice experiment data in Displayr.

Requirements

A document containing a choice-based modeling data set
An appropriate choice model design (see list of formats listed below)

Method

1. From the menus, select Anything > Advanced Analysis > Choice Modeling and select one of the following models:

Hierarchical Bayes - this model is more flexible in modeling the characteristics of each respondent and tends to produce a model that better fits the data
Latent class analysis - to be used when you want a segmentation of respondents
Multinomial logit - equivalent to single-class latent class analysis

A new R output called choice.model will appear on your page.

2. From the object inspector, select one of the following options for the EXPERIMENTAL DESIGN > Design source:

Data set - select variables from a data set to specify the design. Variables need to be supplied corresponding to the version, task and attribute columns of a design. See here for an example.
Experimental design R output - select an R output in the project to supply the choice model design (created using Anything > Advanced Analysis > Choice Modeling > Experimental Design).
Sawtooth CHO format - supply the design using a Sawtooth CHO file. You'll need to upload the CHO file to the project as a data set (first rename it to end in .txt instead of .cho) so that Displayr can recognize it. The new data set will contain a text variable, which should be supplied to the CHO file text variable input.
Sawtooth dual file format - supply the design through a Sawtooth design file (from the Sawtooth dual file format). You'll need to upload this file to the project as a data set. The version, task, and attributes from the design should be supplied to the corresponding inputs (similar to the Data set option).
JMP format - supply the design through a JMP design file. You'll need to upload this file to the project as a data set. The version, task, and attributes from the design should be supplied to the corresponding inputs (similar to the Data set option).
Experiment variable set - supply the design through an Experiment variable set in the project.

3. When Data set, Sawtooth dual file format, or JMP format are selected, choose the variables from your design data set containing the Version, Task, and Attributes.

Note, if you are working with an Alchemer (formerly SurveyGizmo) data set, the ResponseID from the conjoint data set is used as Version and Set Number as Task.

4. You'll also need to provide attribute levels through a spreadsheet-style data editor for most of these options. To enter the attributes, select Enter attribute levels and enter the attribute name and levels in each column:

Note that this is optional for the JMP format if the design file already contains attribute level names. The levels are supplied in columns, with the attribute name in the first row and attribute levels in subsequent rows.

5. Next, you'll need to select the RESPONDENT DATA. Whether respondent data needs to be explicitly provided depends on how you supplied the design in the previous step. If an Experiment Question or CHO file was provided, there is no need to separately provide the data, as Experiment Questions and CHO files already contain the choices made by the respondents.

For the other methods of supplying the design, the respondent Choices and the Tasks or Version corresponding to these choices need to be provided from variables in the project. Each variable corresponds to a question in the choice experiment, and the variables need to be provided in the same order as the questions.

Note the following:

If you have a 'None of these' option, you will need to code this response as 0 or set Missing data to Exclude from analyses for the relevant variables in your data set. See Variable Sets for how to confirm and modify your data.
If you have a dual-response 'none' design, the variables with the dual-response 'none' data must be a Binary - Multi variable set and Count This Value must be selected for the category which indicates that the respondent would purchase their selected choice in Properties > DATA VALUES > Select categories. You will additionally need to select the corresponding 'Yes/No' questions in the Dual-response 'none' choice field.
Note that if your conjoint data comes from Alchemer, see How to Convert Alchemer Conjoint Data for Analysis in Displayr. Displayr will then add the appropriate questions containing the choices and the design version in the respondent data set.
Instead of using respondent data, there is also an option to use simulated data by changing the Data source setting to Simulated choices from priors. See this blog post for more information on using simulated data.

6. Select one of the following options from the Missing data input, which determines how Displayr will deal with missing data, if any:

Use partial data is the default setting which ignores questions with missing data but keeps other questions for analysis
Exclude cases with missing data removes respondents from the analysis if any of the selected questions contain missing data
Error if missing data shows an error message if any respondents have missing data on any of the selected questions

7. In the Model section, if Latent Class Analysis or Hierarchical Bayes is selected as the model Type, enter the Number of classes you want the model to create.

8. OPTIONAL: Enter a value for Questions left out for cross-validation. If there are too many classes, computation time will be long, and the model may over-fit the data. To determine the amount of overfitting in the data, set Questions left out for cross-validation to be greater than the default of 0. This will allow you to compare the output's in-sample and out-of-sample prediction accuracies.

9. All other options are more advanced and will be covered in a different article. These can be left at their default values. If Model is set to Hierarchical Bayes, ADVANCED options become available. These can be left at the default values. For more information see Checking Convergence When Using Hierarchical Bayes for Conjoint Analysis and How to Improve Choice Model Accuracy Using Covariates.

10. OPTIONAL: Apply a filter to the model by selecting filter variable from the Filter(s) input at the top of the object inspector.

11. OPTIONAL: Apply a weight to the model by selecting weight variable from the Weight input at the top of the object inspector.

12. Press the Calculate button to run the model.

How to Change the Specification of a Choice Model

How to Read Displayr's Choice Model Output

How to Remove Random Choosers From a Choice-Based Conjoint Model

How to Create an Experimental Design for Choice-Based Conjoint

How to Set Up a Choice-Based Conjoint Analysis in Qualtrics

How to Preview a Choice-Based Conjoint Questionnaire

How to Compare Multiple Choice Models

How to Create a Utilities Plot

How to Save Utilities From a Choice Model