 Likewise the variation from factor B can be computed as SSB with 1 degree of freedom.The expected value for the mean of the responses in column i is formula_5while the expected value for the mean of the responses in row j is formula_6where i corresponds to the level of factor in factor A and j corresponds to the level of factor in factor B. formula_7and formula_8are main effects.SSA and SSB are main-effects sums of squares.