https://www.surveyking.com/help/conjoint-analysis-explained
A Guide to Conjoint Analysis
Conjoint Analysis Explained: Examples + Survey Template
Definition: Conjoint
analysis is a research technique used to quantify how people value the
individual features of a product or service. A conjoint survey question shows
respondents a set of concepts, asking them to choose or rank the most appealing
ones. When the results are displayed, each feature is scored, giving you
actionable data. This data can help determine optimal product features, price
sensitivity, and even market share.
Why Is It Important? Conjoint analysis goes
beyond a standard rating question. It forces respondents to pick what product
concepts they like best, helping identify what your audience truly values.
Interactive Conjoint Analysis Example Question
Conjoint analysis is used by any company wanting to do
product research; in this example, a restaurant chain. If the chain wanted to
release a new ice cream slot on their dessert menu, conjoint analysis would
help determine optimal flavor, size, and price, like in the example conjoint
survey question below.
If we offered a new menu item for ice cream, which of the
following options would be most appealing to you? Please make one choice per
set. If no options look appealing, choose "None."
Set 1 / 2
|
Option #1
Select
|
Option #2
Select
|
Option #3
Select
|
Select
|
Flavor
|
Vanilla
|
Strawberry
|
Vanilla
|
I would not choose any
|
Size
|
Large
|
Small
|
Large
|
|
Price
|
$2 USD
|
$5 USD
|
$5 USD
|
|
|
Option #1
Select
|
Option #2
Select
|
Option #3
Select
|
Select
|
Flavor
|
Vanilla
|
Strawberry
|
Cookie Dough
|
I would not choose any
|
Size
|
Small
|
Large
|
Small
|
|
Price
|
$5 USD
|
$2 USD
|
$5 USD
|
|
This is an interactive example of choice based conjoint
When to Use Conjoint Analysis
Without conjoint analysis it would be impossible to ask
about product prices along with flavor and size; a separate rating question for
each flavor and size combination is needed. Conjoint analysis solves these
problems with a straightforward survey question. When respondents evaluate this
question, concept features are compared against one another, and a researcher
can identify preferences.
Conjoint analysis is useful in two specific scenarios,
marketing research and pricing analysis.
Marketing Research
Conjoint analysis is used in marketing research to identify
what features of a product or service are most appealing to a customer base.
This research can be conducted on existing products to improve advertising
engagement or identify areas of improvement to increase sales. Conjoint
analysis could also be used to conduct preliminary research for product
feasibility.
A conjoint study will usually include demographic questions
such as gender. A marketing executive can then segment the survey data by
gender, revealing hidden insights used to bolster marketing strategy.
Pricing Research
Conjoint analysis is useful in pricing research because it
forces customers to decide using trade-offs, helping to identify optimal prices
for various levels. The ice cream example we use in this document has a $5 USD
price with the highest utility, which is paired with a "medium" size.
Without a conjoint study, it would have been logical to assume the
"large" size should be sold for $5. Because of the trade-offs, the
optimal size and price combination was found.
How to Conduct a Conjoint Analysis Study
Often, preliminary data needs to be collected before running
your conjoint study. An initial survey would include a MaxDiff or
a Van
Westendorp question to determine important product features or an acceptable
price range. The preliminary survey acts as a baseline to reduce the number of
conjoint concepts. A smaller number of concepts reduces survey fatigue and
increases the quality of responses.
You also want to organize any custom data that you can be
used in the survey. Suppose you want to segment your research by country (USA
vs European customers). In that case, you need to make sure that internal data
is valid, complete, and accessible by your team before running the conjoint
study. If custom data is unavailable, you can add additional questions to the
survey before the conjoint question.
With the preliminary survey data in hand and custom data
organized, you can now create your conjoint analysis study. You can upload the
product attributes and levels, include custom data, and you can add follow-up
questions to ensure a successful project.
Conjoint Analysis Terminology
Conjoint analysis is an advanced research technique that
uses a variety of unique terminology. To help you get a complete understanding,
here is a list of commonly used conjoint terminology:
Attribute
The high-level product features that respondents will
evaluate are called attributes. Attributes are the first column in the above
example question. That example has the following features: flavor, size, and
price. If you studied a new car offering, you might have features such as
color, make, model, MPG, and tire type. There is a limit of 20 attributes on
the SurveyKing platform.
Levels
The items listed within an attribute are called levels. In
the example, the "Flavor" attribute has levels of
"Chocolate," "Vanilla," "Cookie Dough," and
"Strawberry." When you create the conjoint survey, you define an
attribute and the levels that go with each attribute. There is a limit of 15
levels on the SurveyKing platform.
Concept
Combining all your attributes and levels, which creates a
hypothetical product, is called a concept. In the above example, concepts are
the columns that respondents choose. Concepts are sometimes referred to as
"cards" in statistical software. There is a limit of 7 concepts on
the SurveyKing platform.
Set
Also referred to as a task, a set contains multiple concepts
or product offerings. Respondents will choose one concept per set and then be
shown a new set of concepts. There is a limit of 20 sets on the SurveyKing
platform.
Part-Worths/Utilities
This term is the most crucial in conjoint analysis. It
defines how a respondent values each attribute level. When all the utilities
for all respondents are analyzed, a researcher can determine an overall product
value. Utilities are the output of a regression equation.
Utilities have no scale compared to other conjoint projects
you run. They only matter in the context of the current question you are
looking at.
Sometimes utilities are called "part-worths" or
"part-worth utilities." We use the term "utility."
Types of Conjoint Analysis
Choice-Based Conjoint
This is the most common form of conjoint. The example
question above is a choice-based conjoint question. Respondents pick the most
appealing concept for each set. Each set contains a random set of concepts that
are evenly distributed. This type of conjoint best simulates buyer behavior
since each set contains hypothetical products (concepts). When respondents
choose a complete profile, a researcher can calculate preferences from the
tradeoffs made. (e.g even though "Strawberry" isn't a preferred
flavor, if the price were low enough, it would still provide consumer
utility")
As with most conjoint studies, preliminary research is
essential to reduce the number of attributes and levels to choose from. With
fewer attributes and levels, the number of concepts is reduced, which lowers
survey fatigue. A MaxDiff or ranking survey
can be used to find the top four ice cream flavors.
Currently this is the only type of conjoint offered by
SurveyKing.
Best/Worst Conjoint
Sometimes referred to as MaxDiff conjoint. Similar to
choice-based conjoint, this method shows respondents a set of concepts. In each
set, respondents are asked to pick the most/least (or best/worst) concepts.
This approach is used when a product or service has features that cause both
positive and negative reactions. An example could be studying how parents
select daycare. The number of full-time faculty would draw a positive reaction.
The percentage of fellow students that are economically disadvantaged could
produce a negative reaction.
This is a future addition to the SurveyKing platform.
Adaptive Conjoint
This method is also similar to choice-based conjoint.
Respondents pick the most appealing concept for each set, except with this
method, the next set of concepts are not random but are tailored based on the
previous answers. This method is more engaging to respondents and can help
fine-tune the data.
This is a future addition to the SurveyKing platform.
Full-profile conjoint analysis
This method displays many concepts and asks respondents to
rate each one based on the likelihood of purchase. This method is outdated and
was primarily used prior to the introduction of survey tools that offer
choice-based conjoint. Asking to rate lots of concepts at once is
error-prone, quickly causes fatigue, and yields low-quality data.
Rating or Ranking Conjoint
Ranking and rating conjoint was the method used for
full-profile conjoint analysis. As software has progressed, it is now possible
to conduct rating or ranking conjoint similar to a choice-based conjoint.
Respondents are shown a set of concepts and asked to rank or rate each concept.
They could rank by entering a value for each concept, which sums to 100 for
each set, or they could enter a number based on a scale. This method is also
sometimes referred to as "Continuous Sum Conjoint".
Ranking conjoint is a future addition to the SurveyKing
platform.
Menu-Based Conjoint
Menu-based conjoint is a new conjoint method. This method
gives respondents the ability to pick multiple levels from a menu. For example,
a car manufacturer could ask respondents to choose a base model and price, just
like choice-based conjoint. But then they could also ask to check a box for
each additional feature desired such as "Alloy Wheels for $1,500",
"Sunroof for $1,000", or "Parking Assist for $1,500".
This method is much more advanced in terms of front-end
programming and back-end statistics than choice-based conjoint. Often custom
solutions need to be built for a company wishing to create this type of
project.
Creating a Conjoint Survey
Any survey that contains a conjoint question is referred to
as a conjoint survey. SurveyKing currently only offers choice-based conjoint.
Here are the steps needed to create your own conjoint survey:
- Navigate
to the "Builder" page of your survey
- Click on
the "conjoint" element box, drag it into your questionnaire, or
click the "Insert question" dropdown to add a conjoint question
at the end of a specific page.
- To add
a new attribute, click "Add attribute" within the conjoint
builder. The builder will show levels for the attribute to the right of
each attribute.
- Choose
how many sets and concepts you want to display.
- Select
any options to customize the question further.
Conjoint Survey Options
- "None"
choice - This option will add one additional card, or column, per
set that says "None" This option is marked by default. This
setting reflects the real world, where consumers can choose not to buy a
product. You should exclude this setting from projects where customers are
forced to pick an option, such as a government service.
- Reset
choices - With this option, respondents can start back at the
beginning. The respondent will clear all answers for the question, and the
first set will be displayed when the "reset" button is clicked.
We recommend reserving this option for specific circumstances, as it could
lead to second-guessing and low-quality data.
How Many Attributes, Levels, Concepts, & Sets are
Needed?
An ideal conjoint question will have roughly 5 attributes
(rows), 4 concepts per set (columns), and approximately 5 - 10 sets. This will
help ensure respondents are not fatigued. A detailed breakdown is below:
- Attributes -
Roughly 5 attributes with no more than 10 total levels per attribute.
Having fewer levels per attribute ensures the survey will show various
concepts more often.
- Concepts -
Roughly 4 concepts to show each set. Too many concepts per set, and you
risk respondents not making effective choices. The total amount of
concepts available is calculated by multiplying the number of levels in
each attribute. In the example above, we had four flavors, three sizes,
and two prices. Total concepts available would be equal to 4 * 3 * 2 = 24.
Ideally, this number should be no larger than 50. The more total concepts,
the harder it becomes to draw meaningful conclusions.
- Total
Sets - Showing no more than 10 total sets to respondents to avoid
survey fatigue. Generally, 3-5 are best.
How Many Responses are Needed?
We recommend collecting at least 100 responses for each
segment being researched. For example, if you wanted to research both males and
females, you would want to collect 100 responses for both.
Conjoint Analysis Scoring & Results
Conjoint analysis uses regression to calculate how different
attributes and levels are valued.
Because conjoint uses categorical data (a name like ice
cream flavor) instead of continuous data (a number like a temperature), a
particular type of regression is used called logistic regression. Just like any regression equation, the
result of this regression calculates coefficients. These coefficients are
referred to as "utilities".
Utility is not a standard unit of measure. It can be thought
of as "happiness". If a lot of respondents choose concepts containing
"Cookie Dough" and only a few choose concepts with
"Vanilla.", even without doing the math, you can imagine that the
coefficient for "Cookie Dough" would be higher than the coefficient
for "Vanilla."
To illustrate this concept, we ran the above ice cream
example with 20 respondents. Below is the analysis of those responses. This
analysis includes the utilities for each level in addition to the relative
importance of each attribute.
Sample Survey Data - Summary Table
Attribute
|
Importance
|
Level
|
Utility
|
Flavor
|
61%
|
Chocolate
|
Vanilla
|
Cookie Dough
|
Strawberry
|
|
|
Size
|
17%
|
|
|
Price
|
22%
|
|
|
Walking Through the Analysis
The utilities in the last column are the output of
regression analysis. Next to each number is a small bar chart for visual
representation.
Remember, utilities are not an actual unit of measurement
and could be thought of as happiness. If we look at the above table, the
"Cookie Dough" flavor has a utility of 14, and the
"Vanilla" flavor has a utility value of 7. We could interpret this as
"Cookie Dough has double the happiness of Vanilla."
The importance column is the weighted difference in
utilities ranges for the product levels. You can see that flavor has the level
with the largest difference of roughly 7. The larger the utility differences
for an attribute, the more important they are to consumers. To get a
significant difference, as we see with cookie dough, many respondents choose
concepts with that flavor. We know the other levels are evenly distributed,
meaning that cookie dough was a significant driving factor in decision-making
regardless of size or price. Here's how you would calculate the importance:
Take the largest number for each level, and sum:
14.11+4.03+5.06 = 23.02
Divide each of the highest levels by this number. The
calculation for flavor importance is 14.11 / 23.02 = 61%
Overall, it looks like "Cookie Dough" is the
preferred flavor, "Medium" serving size, with a price of "$5
USD". "Vanilla" would also be an excellent addition to the menu
as it brings a high amount of utility. You'll notice that the higher price has
a higher utility value than the lower price. Respondents might have a perception
that a higher cost has a better taste or better quality. The preference for
"Medium" might also be tied to consumers being health conscious. This
summarizes why conjoint is so essential. Not only did we find the two optimal
flavors, but we also found the right size and correct price point. This data
would be almost impossible to capture without conjoint analysis.
Statistical Details
SurveyKing uses ChoiceModelR,
a package in the R statistical program to compute conjoint utilities.
ChoiceModelR calculates a coefficient using logistic regression with the
maximum likelihood for each attribute level by each respondent. When the
analysis is complete, utilities for each level are averaged. The output of our
example can be found in this Excel file.
We color-coded the Excel file for each attribute level. Row
22 has an average subtotal, which the average utility for a specific level. The
regression equations use effects
coding to ensure each attribute in total sums to 0. Because of this,
you will notice the excel file contains negative utilities. We shift each
number by a constant to eliminate negatives and put the baseline to 0. The dark
blue flavor columns were adjusted by 5.43 before the results being loaded into
our dashboard. Having a 0 baseline makes the data easier to interpret.
Data used to populate ChoiceModelR:
- Data
Matrix - See this
Excel file, which is the input for the ice cream example. The first
row of each card set contains the card number chosen (column G). The first
card selected was 4. This is because the "none" option was
selected. When the "none" is the chosen option, the highest index
+ 1 is the card selection. This is the input required for ChoiceModelR.
Other programs use an output similar to this
file. You'll see it's the same setup, except column G has a
"1" if the card is selected or "0" if not selected. An
additional row is added for the none column.
- R -
The total number of iterations of the Markov chain Monte Carlo (MCMC
chain) to be performed. Default value: 4000.
- Use -
The number of iterations to be used in parameter estimation. Default
value: 2000.
- Keep -
The thinning parameter defining the number of random draws to save.
Default value: 5.
- wgt -
the choice-set weight parameter; possible values are 1 to 10. This
parameter only needs to be specified if estimating a model using a share
dependent variable. Default value: 1.
- xcoding -
A number that specifies the way in which each attribute will be coded. We
code each attribute as categorical, which is the value 0. Prices could
technically be labeled as continuous, but for ease of calculations and
consistency, we code all variables are categorical.
Time Spent Per Set
The time spent on each conjoint set is also included in the
results. This data is useful to eliminate low-quality responses. Responses that
answered a set too fast (under 2 seconds) should generally be eliminated from
the results.
Analyzing Concept Profiles
A powerful benefit of conjoint analysis is quantifying how
each concept would fare in the market. We can easily see the product with the
most utility would be Cookie Dough, Medium, for $5 USD. But what about the top
three products? Or the bottom three products? In the ice cream example, there
were 24 hypothetical products. Unique to the SurveyKing platform is the ability
to scroll through each concept in ranked order, to see what profiles faired the
best or worst (or offer the most utility). The reporting section will
automatically include the table shown below:
Rank
|
Flavor
|
Size
|
Price
|
Total Utility
|
1
|
Cookie Dough
|
Medium
|
$5 USD
|
488.02
|
2
|
Cookie Dough
|
Large
|
$5 USD
|
436.91
|
3
|
Cookie Dough
|
Small
|
$5 USD
|
403.10
|
4
|
Cookie Dough
|
Medium
|
$2 USD
|
381.51
|
5
|
Vanilla
|
Medium
|
$5 USD
|
341.31
|
6
|
Cookie Dough
|
Large
|
$2 USD
|
330.40
|
7
|
Cookie Dough
|
Small
|
$2 USD
|
296.58
|
8
|
Vanilla
|
Large
|
$5 USD
|
290.20
|
9
|
Vanilla
|
Small
|
$5 USD
|
256.39
|
10
|
Vanilla
|
Medium
|
$2 USD
|
234.80
|
11
|
Chocolate
|
Medium
|
$5 USD
|
200.82
|
12
|
Strawberry
|
Medium
|
$5 USD
|
191.44
|
13
|
Vanilla
|
Large
|
$2 USD
|
183.68
|
14
|
Vanilla
|
Small
|
$2 USD
|
149.87
|
15
|
Chocolate
|
Large
|
$5 USD
|
149.71
|
16
|
Strawberry
|
Large
|
$5 USD
|
140.33
|
17
|
Chocolate
|
Small
|
$5 USD
|
115.90
|
18
|
Strawberry
|
Small
|
$5 USD
|
106.51
|
19
|
Chocolate
|
Medium
|
$2 USD
|
94.31
|
20
|
Strawberry
|
Medium
|
$2 USD
|
84.93
|
21
|
Chocolate
|
Large
|
$2 USD
|
43.20
|
22
|
Strawberry
|
Large
|
$2 USD
|
33.81
|
23
|
Chocolate
|
Small
|
$2 USD
|
9.38
|
24
|
Strawberry
|
Small
|
$2 USD
|
-
|
To get these figures from the Excel output file, you could
create a table with all possible combinations, and use sumproduct to calculate
to total utility. Here is an example.
Conjoint Analysis by Question Segments
Sometimes it's important to analyze different segments, such
as gender. To do this, add a multiple-choice question to your survey for each
segment you wish to study. In the reporting section, you can choose
"Conjoint Segment Report." From here, select the appropriate
question, and the report will output a data table for each answer. Using the
ice cream example, you may notice "Males" prefer "Cookie
Dough," while "Females" prefer "Vanilla." These are
additional data points to fine-tune your marketing efforts.
Here is an interactive
example of a conjoint comparison report unique to the SurveyKing
platform. The first question asks for gender and the second question asks for a
preferred ice cream concept. You can see males prefer "Cookie dough"
with a utility of 23.06, while females prefer "Vanilla" with a
utility of 25.63. Each gender segment lists flavor as the most important
attribute. The report also includes a segmented ranking of concepts.
Conjoint Analysis Tips
- Keep
descriptions simple - For both attributes and levels, keep the
descriptions as short as possible. This will make picking choices easier
and reduce survey fatigue.
- Images -
Because of limited space, we recommend using images inside of each level
sparingly. When images are used, we recommend that each image be
custom-made for this project with a size no larger than 150px X 150px.
- Additional
descriptions - Let's say you are researching a new phone. If you
have a weight level of 7oz and 11oz, people won't be able to gauge that
difference. You would want to say (ideally in the question text),
"Use the iPhone 7 as a baseline weight, that weight would be
considered average" Then the size product labels would be
"Light," "Average," "Heavier."
- Be
aware of incorrect conjoint content - There is a popular online
video that explains conjoint analysis in Excel. The video uses "Dummy
Variables" to compute the regression. This would be incorrect for two
reasons. Excel cannot do logistic regression without any addons. Also,
removing dummy variables is unnecessary if logistic regression is done
correctly. The video codes a three-level attribute with 1's and 0's, which
results in collinearity. Logistic regression assigns categorical data to a
unique number. Like in our example, a four-level attribute would have the
numbers 1, 2, 3, or 4, depending on what concepts were displayed.