The meaning, classification, and function of natural experiment are illustrated. Natural experiment is compared with traditional experiment and observation, and their similarities and differences are analyzed. Natural experiment utilizes naturally occurring interference or interference caused by others such as treatments, and follows the experimental design of R. A. Fisher. Therefore, natural experiment is not observation in the sense of traditional experiment, is different from the traditional experiment, and is a kind of quasi-experimental between traditional experiment and active observation. At the same time, there is no complete dichotomy between observation and experiment, but there is a continuous series, namely passive observation, active observation, natural experiment, and traditional experiment according to presence or absence of interference, the interference imposer, and the availability of experimental design.

ecology  /  natural experiment  /  scientific methodology