實驗法是社會科學中用以釐清變項間因果關係的主要研究方法。作者應《體育學報》之邀撰文，探討實驗法之原理，及其在體育及運動相關研究上的應用。本文首先介紹因果推論成立的條件，包含先行（precede）、相關（correlation）、及虛假性（spurious）（Simon, 1954）。然後以此為基礎，說明二種主要的實驗設計：受試者間設計（between subjects design）和受試者內設計（within subjects design）之原理，及其為何可以達成因果推論。此外本文亦介紹體育研究中常用的類實驗設計（quasi-experimental design），說明在類實驗設計下如何克服可能的研究限制。最後，由於一般研究方法著作中，對如何操作實驗的具體細節少有論述，本文亦針對實際操作實驗時應注意的事項提出建議，供體育相關研究者之參考。

The author was invited by Physical Education Journal to introduce the principles of experimental design and its application in sport and physical education research. This article first introduced the conditions of establishing casual relationship, including precede, correlation, and spurious (Simon, 1954). Then, two major experimental designs, between- and within- subjects design, were introduced. The author explained how these designs can help in revealing casual relationship by either random assignment (fro between subjects design) or order balance (for within subject design). Quasi-experimental design, its limitation, and remedy were also introduced. Finally, the author also provided some practical guidelines for conducting experiment.