PsychStatsWiki

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ANOVA无法说明哪个备择假设得到支持；
- The ANOVA cannot indicate which alternative hypothesis is supported.

要进行事后检验以说明各组差异在什么地方；
- Post-hoc tests are needed to show where the groups differ.

事后检验是比较每一个组和另一个处理组，一次比较两个，这称为成对比较。
- Post-hoc test compares each group to another treatment group, two at a time; this is called a pairwise comparison.

每一个比较都是一个单独的假设检验，每一个都有犯I类错误的风险。所以，比较对数越多，作结论的风险越大。即容易发现实际不存在的差异。这称为实验导致的（experimentwise）alpha水平或族系（familywise）误差；
- Each comparison is a separate hypothesis test, each with the risk of making a Type I error. So the more pairs of comparisons there are, the greater the risk of making a conclusion. That is, it is easy to find differences that do not actually exist. This is called the experimentwise alpha level or familywise error.
多次比较后犯I类错误的概率为α<sub>EW<sup/>=1-(1-α）c，其中c为比较的次数。