I asked participants of a survey to rate the competence of 10 stimuli and want to see whether the stimuli differ significantly. I conducted a repeated measurements ANOVA and tested whether competence ratings significantly differs as a function of stimuli. It was not significant. Then I excluded two stimuli from the ANOVA and it became significant. How is that possible?
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Possible duplicate of [How to test the statistical significance for categorical variable in linear regression?](http://stats.stackexchange.com/questions/31690/how-to-test-the-statistical-significance-for-categorical-variable-in-linear-regr) – kjetil b halvorsen Feb 27 '17 at 16:15
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1@kjetilbhalvorsen, the questions are clearly *related*, but I'm not sure that's an obvious duplicate. – Matt Krause Feb 27 '17 at 19:55
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Then there are other very similar posts which are better candidates for duplicates! – kjetil b halvorsen Feb 27 '17 at 20:02