Multimodal Distribution

Multimodal distribution is a distribution that has multiple modes (thus two or more "peaks").

Multimodality of the distribution in a sample is often a strong indication that the distribution of the variable in population is not normal. Multimodality of the distribution may provide important information about the nature of the investigated variable (i.e., the measured quality). For example, if the variable represents a reported preference or attitude, multimodality may indicate that there are several pronounced views or patterns of response in the questionnaire. Often however, the multimodality may indicate that the sample is not homogenous and the observations come in fact from two or more "overlapping" distributions. Sometimes, multimodality of the distribution may indicate problems with the measurement instrument (e.g., "gage calibration problems" in natural sciences, or "response biases" in social sciences).

See also, unimodal distribution and bimodal distribution.