observational study
A research method in which subjects are observed without intervention, commonly used in epidemiology and social sciences.
In this observational study, the participants' lifestyle habits were tracked over a long period.
実験的研究 involves intervention by the researcher, while 観察的研究 only observes without manipulation.
Compound of 観察 (observation) + 的 (-ive) + 研究 (research). A straightforward modern technical term.