Over recent months we have helped a social housing provider come up with new home designs using Maximum Difference (MaxDiff) Scaling.
MaxDiff is a technique for measuring the importance or preference of multiple items. In MaxDiff tasks, respondents see sets of items (typically 4 to 6). In each set, respondents indicate which item is most important (preferred) and least important (preferred).
MaxDiff is shown to provide results that have greater between-item and between-respondent discrimination, and greater predictive accuracy than either monadic ratings or paired comparisons.
Asking respondents to rank large numbers of items is unreliable, as is asking a scale question for each item.
Ranking tasks become difficult to manage when there are more than about seven items, and the resulting data is on an ordinal scale only.
Rating tasks assume that respondents can communicate their true affinity for an item using a numeric rating scale. Rating data is often negatively affected by lack of discrimination among items and scale use bias (the tendency for respondents to use the scale in different ways, such as mainly using the top or bottom of the scale, or tending to use more or fewer available scale points).
MaxDiff questionnaires are relatively easy for most respondents to understand. Furthermore, humans are much better at judging items at extremes than in discriminating among items of middling importance or preference. Also since the responses involve choices of items rather than expressing strength of preference, there is no opportunity for scale use bias.
After analysis, MaxDiff produces a rank between the items tested plus a metric distance between the items.
The output for a MaxDiff exercise is an interactive Excel tool. This can be customised to suit the clients’ requirements. Filters can be added to the tool so that comparisons may be made across different sub-samples.