Kostenloser Odds Ratio Rechner
Berechnen Sie den odds ratio aus a 2x2 table. Compare odds of an outcome between two groups. Kostenloser OR Rechner.
Odds Ratio (OR)
2.4286
Odds Ratio (OR) vs Group 1 - Event (a)
Formel
## 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.
Lösungsbeispiel
Group 1: 30 events, 70 non-events. Group 2: 15 events, 85 non-events.
- 01Odds Group 1 = 30/70 = 0.4286
- 02Odds Group 2 = 15/85 = 0.1765
- 03OR = (30*85) / (70*15) = 2550 / 1050 = 2.4286
- 04ln(OR) = ln(2.4286) = 0.887
- 05The odds of the event are 2.43 times higher in Group 1
Häufig Gestellte Fragen
How does odds ratio differ from relative risk?
The odds ratio compares odds (event/non-event), while relative risk compares probabilities (event/total). For rare events (< 10%), OR approximates RR. For common events, OR exaggerates the association.
Why is the log of OR used?
The log odds ratio has better statistical properties: it is symmetric around 0 (OR=1), approximately normally distributed, and is used in logistic regression. Confidence intervals are computed on the log scale then exponentiated.
Can the odds ratio be zero or negative?
The OR is always positive (since all cells are non-negative counts). It can be zero only if a = 0 or d = 0 (no events in one cell). It can never be negative.
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