Introduction to Between-Subjects Analysis of Variance: Preliminaries (1 of 4)

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Analysis of variance (ANOVA) is used to test hypotheses about differences between two or more means. The t-test based on the standard error of the difference between two means can only be used to test differences between two means. When there are more than two means, it is possible to compare each mean with each other mean using t-tests. However, conducting multiple t-tests can lead to severe inflation of the Type I error rate. (Click here to see why) Analysis of variance can be used to test differences among several means for significance without increasing the Type I error rate. This chapter covers designs with between-subject variables. The next chapter covers designs with within-subject variables.

Consider a hypothetical experiment on the effect of the intensity of distracting background noise on reading comprehension. Subjects were randomly assigned to one of three groups. Subjects in Group 1 were given 30 minutes to read a story without any background noise. Subjects in Group 2 read the story with moderate background noise, and subjects in Group 3 read the story in the presence of loud background noise.
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