
Calculation Scheme:

Each picture is a snapshot of the way the RippleSoftware tool "Teaching Statistics" shows the meaning of the ANOVA Sum of Squares
Calculation of the Total Sum of SquaresTo determine the Total SS in an ANOVA: (1) find the mean of all the scores; (2) find the deviation of each of the scores from the overall mean; (3) square each of the deviation scores; and (4) add them up. 
Calculation of the Within Groups Sum of SquaresTo determine the Within Groups SS in an ANOVA: (1) for each level of the independent variable, find the group mean; (2) find the deviation of each of the scores in a group from that group's mean; (3) square each of the deviation scores; and (4) add them up. 
Calculation of the Between Groups Sum of SquaresTo determine the Between Groups SS in an ANOVA: (1) find the mean of all the scores; (2) find the mean of each of the groups; (3) calculate the difference between each of the group means and the overall mean; (3) write down each of the groupmeandeviations the same number of times as there were subjects in the group; (4) square the deviations and then add up the squared deviations. 
©20042006 by Burrton Woodruff. All rights reserved. Modified