How To Built A Choice Based Conjoint Questionnaire Using Eyequestion
What is Choice-Based Conjoint Analysis?
Choice-Based Conjoint Analysis is a sophisticated market research technique used to decipher consumer preferences. It simulates real-world buying scenarios by presenting respondents with a series of choices, each representing different combinations of product attributes. By analyzing how individuals make choices within these scenarios, businesses can derive valuable insights into the relative importance of various product features and their impact on purchasing decisions.
In this article, we will walk you through the entire process, from designing a Choice-Based Conjoint questionnaire in EyeQuestion to performing advanced conjoint analysis using EyeOpenR.
Create a Project
Start by creating a project. To do this, click on "Project" and then select "Create Project."
Choose the "01 STANDARD with Experimental Design Template."
Design Configuration
Once your project is open, navigate to the "Design" section.
In the "Design" section, locate the "Generate design" option.
Choose "Conjoint analysis" as the design type.
Fill in Design Details
Provide the following information for your conjoint analysis setup:
Number of Trials per Set/Subject: This determines how many combinations of product concepts, that together form a choice task, will be presented to each panelist (maximum = 15).
Number of Product Concepts for Each Trial: Specify how many different product concepts will be presented simultaneously to panelists to choose from in each choice task (maximum = 5).
Sets/Subject: Determine the number of sets to be created based on the number of subjects in your test. A minimum of 100 sets is recommended (maximum = 250).
Image Attribute: Select the images to be included in creating the product concepts. You can upload images by clicking on the image icon (if you do not wish to use images in your product concepts simply do add any images to these fields).
Attribute: Define the name of the attribute and specify the alternative forms (levels) this attribute can take within your study. Product concepts will be formed by combining different combinations of attribute levels e.g. in the below screen shot one product concept could consist of Image 1 and Vegan = No (Maximum: Attributes = 5; Levels = 5).
Generate Design
Once you have set all the information about your conjoint design, click on the "Generate" button.
Note that if the design is extensive and requires many sets to be created, it may take some time to create the design.
After the design is generated, you will find all the product concepts stored in the product information section. It's important not to alter the product information once the design is generated. If you need to make modifications to the design, simply generate a new conjoint design instead. Due to the size of the designs generated in conjoint studies it is not possible to view the design in the 'Design Sets' table within EyeQuestion, instead you can find here a link to the Export page on which you can download your design in various formats.
Add a Choice-Based Conjoint Question
As a continuation of building your conjoint questionnaire design, you will need to add a "Choice-Based Conjoint" question to your questionnaire. To do this proceed to the design section and select the "Choice-Based Conjoint" question type to add.
When you select the 'Choice-Based Conjoint' question type in the design section, it will automatically incorporate all the information derived from the design you generated earlier. Additionally, within this question type, you have the flexibility to rearrange the attribute order as it will be presented to panelists and even choose to include a 'none' option within the questionnaire. The 'None' option allows the panelist to not choose any of the presented product concepts and instead click 'None' when presented with each choice task.
NOTE: Although you can add further questions to your project, it is not currently possible to have both Multi-Sample enabled questions and 'Choice-Based Conjoint' questions within the same project (although this functionality may be possible in future releases of EyeQuestion).
Data Analysis
Once you have collected your data, you can proceed to analyze it using EyeOpenR, for which we have a specific method for analysing choice-base conjoint data. To do this, navigate to the "Method" tab and select "Conjoint analysis."
Within EyeOpenR the analysis of results from choice based conjoint studies is performed using Hierarchical bayes multinomial logit models with MCMC used to generate model estimates. This is implemented using the choicemodelR R package (Sermas, 2012).
NOTE: The choiceModelR function requires at least one data point for each possible display location in the design. In other words, should your design present three product concepts per trial, on each trial a different product will be presented in each of three possible display locations. In the resulting dataset any panellist must have chosen any product at least once in all three of the possible display locations. If the dataset does not meet this constraint the analysis will not run in EyeOpenR and an error message explaining this issue will be presented to the user in EyeOpenR in the ‘Information’ table.
Options within EyeOpenR
You are presented with the following options before the choice based conjoint analysis is performed:
Choice Based Conjoint Question: You can select from a drop down list the conjoint question you wish to analyse (the drop down list contains all the questions within your project)
Number of decimal places: Defines the number of decimal places returned in the results tables (excl. Utility Estimate Distributions)
Do your results include a none option?: You can indicate whether the ‘None’ option is included in yours results and therefore was available to panelists when selecting from their choice of product concepts.
Results of Conjoint Analysis within EyeOpenR
The analysis performed on your conjoint data within EyeOpenR generates, for each Judge|Panelist in your dataset, a utility estimate (the average of MCMC draws of unit-level model coefficients) corresponding to each attribute level within your design. This utility estimate can be viewed as an estimate of the weight applied by an attribute level to a given choice decision, with positive values increasing the likelihood of choosing a product with the given attribute level, and conversely negative values reducing the likelihood of choosing a product with the given attribute level.
The results of the above analysis are presented on four separate tabs within EyeOpenR, with each tab presenting distinct measures, each derived from the utility estimates but offering different insights into the results of your study. The information presented on each of these tabs is described below:
Attribute Importance
This records the relative importance of each attribute within the design. Attribute importance is returned as two measures (in the below description the utility estimate is the summed utility estimate across all Judges|Panelists):
Importance: This can be interpreted as representing the relative importance attributed to a given attribute when panelists made their choices in your study. It reflects the distance between the largest and smallest utility estimate for levels within an attribute.
Percentage: This is simply the relative importance of the given attribute presented as a percentage relative to all other attributes in your study. This is derived as follows: (Importance for given attribute / (sum of importance of all attributes)) * 100.
Utility Estimate Distributions
The chart displayed here indicates the level to which your panelists agree or differ in the influence of each attribute. A distribution is displayed for each attribute level in your study. A distribution with a single high peak indicates your panelists were largely influenced in their choices in the same way by the given attribute level. Whereas if the distribution is spread widely across the parameter space then this indicates there was little similarity across you panelists in how this attribute level influenced their choice. It is also possible that you see multiple peaks for a given attribute, this suggests that within your study distinct groups of panelists exist in which the same attribute level influenced each group differently. More specifically, the table returned here, from which the distributions are derived, contains the utility estimate for each Judge|Panelist for each level of each attribute. The chart displays a plot for each attribute level, reporting how the various Judge|Panelist estimates are distributed across the Utility parameter space (distributions are constructed using Gaussian Kernel Density Estimation). Across all plots increased utility indicates a Judge|Panelist is more likely to choose a product with this attribute level.
Sensitivity: Attribute Level Utilities
The chart displayed here shows the influence of each attribute level on the choices made by all panelists in your study. A larger attribute level utility indicates that panelists were more likely to chose a product containing this attribute level. While conversely a smaller utility value indicates panelists were less likely to chose a product containing this attribute level. The attribute level utilities are simply the sum across all Judges|Panelists of the utility estimates for the given attribute level.
Market Performance by Product Concept
This table can be interpreted as representing all product concepts in terms of most likely to least likely to be chosen. This table contains all possible product concepts within the project design ranked from largest to smallest in relation to a product’s Total Utility where Total Utility is simply the sum of attribute level utility estimates for all levels that define the given product concept.
Information
This table records any error messages and/or warning messages generated when analyzing your data.
If there are no data points within the data set for any one of the display locations (see above NOTE) the analysis will not run and therefore the following error message will appear in the information table providing explanation “The following display locations were never selected: [DISPLAY LOCATIONS]. In your dataset each location must have been selected at least once in order to run this analysis.”.
If you have indicated that a none option is present in your design [see 'Options within EyeOpenR' section above] but no none option is detected in the data set then the following warning message is displayed in the information table "WARNING: None option not recorded in dataset and therefore not included in analysis". Conversely if you have indicated that there is no none option present in the design yet a none option is detected in the dataset the following warning message will appear in the information table “WARNING: None option was recorded in dataset and therefore included in analysis".
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