The combination of methodologies in the study of the same phenomenon or construct; a method of establishing the accuracy of information by comparing three or more types of independent points of view on data sources (for example, interviews, observation, and documentation; different investigations; different times) bearing on the same findings.
There is a method of establishing the accuracy of information by which one compares multiple types of independent viewpoints on sources of data and reaching the same conclusion.
It does no good to compare more than three types of independent viewpoints on data sources.