The Analysis of Variance (ANOVA): comparing differences of 3 or more groups


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The Analysis of Variance is used to determine if there is a significant difference between more than two groups in terms of a variable. Because a t-test can only be done for two groups, in cases that there are three or more groups, it is more practical to use ANOVA instead of conducting a series of t-tests for several pairs of groups.

There are several types of ANOVA. The simplest one is the one way analysis of variance.

In the following example we will try to compare the Biological Oxygen Demand (BOD) of three hypothetical lakes using One Way Analysis of Variance.


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