统计显著性、效果大小与效力分析.ppt

Lecture 11 Psychology 203 Psychology 203 - 2007 Lecture 11 - Effect Size Statistical Power 主要内容 数据处理与分析 了解数据的一般特征，如数据分布等。 通过数字、图示和文字对数据进行概括，集中与离散趋势，效应大小等。 验证研究假设。 假设检验的逻辑与局限 效应大小的概念、计算与意义 效力的概念、影响因素与意义 The Key Elements of Hypothesis Testing The Key Elements of Hypothesis Testing Types of Statistical Error a few words on hypothesis testing… 心理科学研究是一个对不确定问题的决策过程，是通过风险决策获得进步的。 Accept H1 and reject H0 Reject H1 and ‘accept’ H0 但是，拒绝H0，并意味着H1一定为真!也不意味着差异（或效应）一定具有实际意义!! 同样，没能拒绝 H0 do也不意味着 H0 一定为真! 没有获得证据不是没有差异（或效应）的证据（Absence of evidence is not evidence of absence） Criticisms of Hypothesis Testing An all or none decision e.g. z = 1.90 is not significant, whereas z = 2.0 is! 1.90 is so close! but we often have to draw a line in the sand somewhere, when making decisions… More criticisms of Hypothesis Testing We can’t answer the question we want to We can’t say whether the null hypothesis is true or false E.g. Assume Treatment X really always has an effect, however small. If so, then H0 is always false But we are unable to show that H0 is false (or to show that is true) We can only show that H0 is very unlikely The question we can answer is about our data, not H0, i.e how likely is the data we got, if H0 is true Significant does not necessarily mean significant! The manufacturers of Herbalift（康保莱）, herbal supplement, insist that University Tests show that their product will give you significantly more energy in your daily life. Doesn’t this guarantee you’ll notice an increase in your energy levels? Not necessarily! The effect can be tiny and still be significant! Statistical significance does not mean an effect is big or important. Why is this so? Testing Herbalift The average daily energy level of an UWA Uni student aged between 18 and 25 is rated as 60%, with an sd of 10% A sample of 500 students try Herbalift for a month and their average daily energy levels are 62% Is this 2% improvement significant? z-test of Herbalift ?=60,?=10, M=62, n=500 Calculate Standard