Table 2.

Simulation results

Confounding	Non-candidate Inclusion	n	Purposeful	Stepwise	Backward	Forward
20	0.1	60	5	3.6	6.3	9.1
		120	17.3	15.6	18.2	18.8
		240	39.7	39.6	40.1	30.3
		360	55.2	54.4	54.4	36.6
		480	64.3	64.3	64.3	37.5
		600	65.8	65.7	65.7	41.3
20	0.15	60	9.2	4.6	6.4	8.1
		120	18.7	14.8	17.2	18.5
		240	43.1	37.1	38.2	30.5
		360	56.5	53.7	53.9	37
		480	63.6	62.6	62	43
		600	70.3	69	68.7	41
15	0.1	60	6.6	4.1	6.1	9.6
		120	17.8	15.6	18.6	19.2
		240	39.7	36.6	37.6	29.8
		360	53.3	52.2	52.6	38.3
		480	62.4	62.1	62.1	40.1
		600	68.5	67.9	68	40.2
15	0.15	60	9.7	4.4	6.7	9
		120	21.9	16.8	21.3	19.6
		240	46.6	40.2	41.4	32.3
		360	57.7	52.5	52.5	35.3
		480	64	63.1	63.1	39.3
		600	70.4	69.6	69.6	41.4

Retention of the correct model for purposeful, stepwise, backward, and forward selection methods, under 24 simulated conditions that vary confounding, non-candidate inclusion, and sample size levels.