勝算比(odds ratio)

1.勝算 (Odds) 發生某事件的人數與未發生該事件人數的比值
2.勝算比 (Odds Ratio, OR) (在病例對照研究中) 實驗組中發生疾病的勝算與控制組中發生疾病的勝算比值, 或罹患疾病的病患暴露於某變因的勝算除以控制組暴露的勝算
示範

	Adverse event occurs (Disease)	Adverse event doesn't occur (non Disease)	Totals
Exposed to Treatment  (實驗組)	1  a	19 b	20 a+b
Not Exposed to Treatment (對照組)	4 c	16 d	20 c+d
	5 a+c	35 b+d	40 a+b+c+d

EER = a/(a+b) = 1/20 = 0.05

CER = c/(c+d) = 4/20 = 0.20

Experimental event odds = a/b = 1/19 = 0.053

Control event odds = c/d = 4/16 = 0.25

Relative risk = EER/CER = 0.05 / 0.20 = 0.25

Relative odds = odds ratio = (a/b) / (c/d) = ad/bc = 0.21

資料來源：馬偕紀念醫院HomeAny source