Table 3.

Study power: hazard ratio detectable (power 80%, P<.05, 2-sided) under different population size and exposure prevalence scenarios.

Strata	Study population (N)	Scenarios for attention-deficit/hyperactivity disorder						Scenarios for type 1 diabetes								Scenarios for inflammatory bowel disease
		Cases (n)	Exposure prevalence (hazard ratio)					Cases (n)		Exposure prevalence (hazard ratio)					Cases (n)			Exposure prevalence (hazard ratio)
			50%	33%	10%	5%			50%		33%	10%	5%				50%		33%	10%	5%
All	300,000	1000	1.2	1.2	1.3	1.5	400		1.3		1.4	1.5	1.7	200			1.5		1.5	1.7	2.0
Sex	150,000	500	1.3	1.3	1.5	1.6	200		1.5		1.5	1.7	2.0	100			1.7		1.7	2.0	2.4
Ethnicity	60,000	200	1.5	1.5	1.7	2.0	80		1.8		1.8	2.2	2.5	40			2.2		2.2	2.7	3.2