Table 1. Contingency tables and procedure for Chi-squared test.

	Observed frequency (O)				Expected frequency (E)			O − E			(O − E)2 / E
Example 1		A	B	Total	A	B	Total	A	B	Total	A	B	Total
	Male	50	50	100	50	50	100	0	0	0	0	0	0
	Female	50	50	100	50	50	100	0	0	0	0	0	0
	Total	100	100	200	100	100	200	0	0	0	0	0	0
Example 2		A	B	Total	A	B	Total	A	B	Total	A	B	Total
	Male	30	70	100	30	70	100	0	0	0	0	0	0
	Female	30	70	100	30	70	100	0	0	0	0	0	0
	Total	60	140	200	60	140	200	0	0	0	0	0	0
Example 3		A	B	Total	A	B	Total	A	B	Total	A	B	Total
	Male	30	70	100	50	50	100	−20	20	0	8	8	16
	Female	70	30	100	50	50	100	20	−20	0	8	8	16
	Total	100	100	200	100	100	200	0	0	0	16	16	32