Once we have obtained the between-groups sums of squares, we break this estimate down into its relevant components -- main effects for Factor A (Severity of Crime) and Factor B (Time of Testing) as well as the interaction between the two effects (Severity x Time). We begin with the main effect for Factor A (Severity of Crime).

Formula

Using the sums of raw scores from the design table, set up the equation. Notice that we combine the scores from each level of the factor as we set up the equation. Then proceed with the calculations.