Table : TABLE 12-6. Calculating the Within-Groups Sum of Squares The within-groups sum of squares is calculated by taking each score and subtracting the mean of the sample from which it comes—not the grand mean—to create deviations, then squaring the deviations and summing the squared deviations.

Sample	X	(X − M)	(X − M)²
Foraging	28	−5.25	27.563
	36	2.75	7.563
M_for = 33.250	38	4.75	22.563
	31	−2.25	5.063
Farming	32	−3.000	9.000
	33	−2.000	4.000
M_farm = 35.000	40	5.000	25.000
Natural resources	47	−0.333	0.111
	43	−4.333	18.775
M_nr = 47.333	52	4.667	21.781
Industrial	40	−4.000	16.000
	47	3.000	9.000
M_ind = 44.000	45	1.000	1.000
	GM = 39.385		SS_within = 167.419