MaxDiff is a survey research technique for working out relative preferences. What do people like most? Second-most? Etc. It is useful in situations when simpler techniques – such as asking people to rate things or provide rankings – are considered likely to give poor data. It is also known as maximum difference scaling and best-worst scaling.
Example of a MaxDiff question
A MaxDiff study involves presenting a sample of respondents with a series of questions, in which each question contains a list of alternatives. Respondents are asked which alternative they like the most (best) and which the least (worst). The list of alternatives changes from question to question. I've provided an example, below.
Why do people use MaxDiff?
MaxDiff is used to resolve two practical problems with traditional rating scales:
- Poor discrimination between alternatives, with respondents in surveys, often rating multiple alternatives as very important, or 10, on a 10-point scale
- Yeah-saying biases, which are a type of response bias, whereby some respondents typically give much higher ratings than others
Consider the problem of working out what capabilities people would most like in the President of the United States. Asking people to rate the importance of each of the following characteristics would likely not be very useful. We all want a decent and ethical president. But we also want a president who is healthy. And the President needs to be good in a crisis.
We would end up with a whole lot of people rating the capabilities as 10 out of 10 for importance. Some people may give an average rating of 9, whereas others may give an average rating of 5, just because they differ in terms of how strongly they like to state things. MaxDiff is ideal in these kinds of situations.
Overview of the process when doing a MaxDiff study
There are five stages in a MaxDiff study:
- Creating a list of alternatives
- Creating an experimental design
- Collecting the data
- Statistical analysis
Outputs from a MaxDiff study
The end-point of a MaxDiff study is usually one or both of the following:
- A ranking of alternatives in order of preference. For example, if the study is being used for product-concept testing, the goal is to work out the relative appeal of the concepts.
- An understanding of differences between people in terms of their preferences for the alternatives. For example, a study examining preferences for product attributes may be designed as an input to a segmentation exercise, looking to find segments of people with different preferences.