Table : TABLE 12-8. The Three Sums of Squares of ANOVA The calculations in ANOVA are built on the foundation we learned in Chapter 4, sums of squared deviations. We calculate three types of sums of squares, one for between-groups variance, one for within-groups variance, and one for total variance. Once we have the three sums of squares, most of the remaining calculations involve simple division.

Sum of Squares	To calculate the deviations, subtract the…	Formula
Between-groups	Grand mean from the sample mean (for each score)	SS_between = Σ(M − GM)²
Within-groups	Sample mean from each score	SS_within = Σ(X − M)²
Total	Grand mean from each score	SS_total = Σ(X − GM)²