Odds Ratio
Compare event odds across two independent groups.
Your numbers
Odds ratio
Use positive cell counts. The large-sample interval can be unreliable for small samples; no continuity correction is applied.
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Formula
Use OR = ad/(bc) and bounds exp[ln(OR)±1.96√(1/a+1/b+1/c+1/d)]. a and b are group A event and non-event counts; c and d are group B counts. The logarithmic interval uses a normal approximation and requires positive counts.
Compare event odds across two independent groups.
Worked example
- A events
- 20
- A non-events
- 80
- B events
- 10
- B non-events
- 90
- Odds ratio
- 2.25
- Approximate 95% lower bound
- 0.994294892282
- Approximate 95% upper bound
- 5.09154782882
Scope and limitations
Use positive cell counts. The large-sample interval can be unreliable for small samples; no continuity correction is applied.
Inputs are checked for missing values and allowed ranges. A result outside the finite numeric range is not displayed. Rounding affects display, while the calculation uses the model’s numeric precision.
Check your units and assumptions before relying on a result. Changing a label does not convert a currency or physical unit.
Formula version: 6ac9e776e9af · Example checked: