Odds Ratio Calculator — Formule
## How to Calculate the Odds Ratio
### Formula
**OR = (a * d) / (b * c)**
where a, b, c, d are cells of the 2x2 table:
- a = exposed cases, b = exposed non-cases
- c = unexposed cases, d = unexposed non-cases
OR = 1 means no association. OR > 1 means the exposure increases the odds of the outcome. OR < 1 means the exposure is protective.
### Formula
**OR = (a * d) / (b * c)**
where a, b, c, d are cells of the 2x2 table:
- a = exposed cases, b = exposed non-cases
- c = unexposed cases, d = unexposed non-cases
OR = 1 means no association. OR > 1 means the exposure increases the odds of the outcome. OR < 1 means the exposure is protective.
Exemple Résolu
Group 1: 30 events, 70 non-events. Group 2: 15 events, 85 non-events.
- Odds Group 1 = 30/70 = 0.4286
- Odds Group 2 = 15/85 = 0.1765
- OR = (30*85) / (70*15) = 2550 / 1050 = 2.4286
- ln(OR) = ln(2.4286) = 0.887
- The odds of the event are 2.43 times higher in Group 1