Ecological validity

In research, the ecological validity of a study means that the methods, materials and setting of the study must approximate the real-world that is being examined. Unlike internal and external validity, ecological validity is not necessary to the overall validity of a study.

Ecological validity is often confused with external validity--the property of a measurement process that reflects our ability to generalize from a study's results to circumstances beyond the research setting. While the two forms of validity are closely related, they are independent—a study may possess external validity but not ecological validity, and vice versa. For example, mock-jury research is designed to study how people might act if they were jurors during a trial, but many mock-jury studies simply provide written transcripts or summaries of trials, and do so in classroom or office settings. Such experiments do not approximate the actual look, feel and procedure of a real courtroom trial, and therefore lack ecological validity. The better recognized concern is that of external validity: if the results from such a mock-jury study are reproduced in trials where the conditions are better controlled, then the measurement process may be deemed externally valid. However, an ecologically valid measurement of a variable in a simulated environment is intended to result in results that can be generalized to real-life situations. Improving the ecological validity of an experiment typically improves the external validity as well.

The original meaning of 'ecological validity' defines it more narrowly as a property of stimuli in perceptual experiments. The popular use, broadly equivalent to 'realism', has overtaken it, at least in A Level Psychology circles. 'Representative design' captures the popular usage of ecological validity and can be used in its place.

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