Odds Ratios (OR) versus Risk Ratios (RR)

	Disease	No disease	Total	Risk of disease	Odds of disease
Exposed	a	b	a+b	a/(a+b)	a/b
Unexposed	c	d	c+d	c/(c+d)	c/d
Odds Ratio				(a/b)/(c/d)
Risk Ratio				(a/(a+b))/(c/(c+d))
	Disease	No disease	Total	Risk of disease	Odds of disease
Exposed
Unexposed
Odds Ratio
Risk Ratio