研究設計應如何考慮統計考驗力

The Power of Statistics in the Design of a Study

進行研究時，先評估研究的統計考驗力是很重要的。一個研究的統計考驗力(statistical power）與研究樣本的大小、效果大小(effect size）、第一類型錯誤率、及所採用的統計考驗方法有關。本文即以兩篇實徵性研究為例，透過檢視其樣本大小，所用的統計考驗，處理效果，測量工具，與組內的變異等，分別分析其第一類型錯誤及第二類型錯誤的可能性。最後建議，以下列方式提高統計考驗力：研究前先分析統計考驗力、提高可操作性的效果大小、增加研究樣本、決定適當的第一類型錯誤率、以及採用妥適的統計考驗方法。

An analysis of the power of the statistical methods used is very important in designing any research project or investigation. The major concepts regarding statistical power include the sample size of the study, the desired detectable effect size, the specified Type I error rate, and the sensitivities of statistical testing. The purpose of this article is then to explain the procedures a researcher should employ in order to make such statistical power explicit in the design of his or her study. Two empirical investigations are described in order to illustrate Type I and Type II error by examining sample size, statistical tests, measures, treatment effects, and variability within the subject groups of these tow studies. Finally, some procedures for the consideration of statistical power in experimental design are suggested.