A customer satisfaction model developed by Japanese research Noriaki Kano in the early 1980s. Kano analysis is a set of ideas and techniques that help determine perceived user satisfaction with product features (e.g., product backlog items). Kano analysis uses a questionnaire were customers are asked both a functional (“How would you feel if the feature is included?”) and dysfunctional (“How would you feel if the feature were not included?”) form of a question about individual features. Based on how users answer these questions, Kano analysis classifies a feature as either mandatory (has to be in the product), linear (customer satisfaction will be linear with increases in quantity or quality of the feature), or exciter/delighter (customer satisfaction will be very high since customers didn't even know they wanted this feature until they saw it, and now they believe they can't live without it). Kano model analysis is one technique that can be used to determine the level of investment (if any) to make in each product backlog item and therefore is a technique that can be used to help prioritize product backlog items.