ANOVA

The basic idea underlying ANOVA relies on an important theorem in mathematical statistics which states that the total variance of the pooled sample can be divided into two components: the within groups variance and the between groups variance.

The within groups variance is simply the sum of the variances calculated for the individual groups; the between groups variance is the variance obtained using the means of each group as data. The within groups variance represents the internal variability of the groups; the between groups variance measures how well separated these groups are.



Medical statistics, Kirkwood, B, Blackwell Science publishing, 2003
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