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Odds Ratio Formula:
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Odds Ratio (OR) is a measure of association between an exposure and an outcome. It represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.
The calculator uses the Odds Ratio formula:
Where:
Explanation: The formula calculates the ratio of the odds of an event occurring in the exposed group versus the odds of it occurring in the non-exposed group.
Details: Odds Ratio is widely used in case-control studies, clinical research, and epidemiology to quantify the strength of association between risk factors and outcomes. It helps researchers understand relationships between variables and make informed decisions.
Tips: Enter the four cell counts from your 2x2 contingency table. All values must be non-negative integers, and the product of b and c must not be zero to avoid division by zero.
Q1: What does an OR of 1 mean?
A: An OR of 1 indicates no association between exposure and outcome - the odds are equal in both groups.
Q2: What does an OR greater than 1 indicate?
A: An OR > 1 suggests increased odds of the outcome occurring with exposure compared to without exposure.
Q3: What does an OR less than 1 indicate?
A: An OR < 1 suggests decreased odds of the outcome occurring with exposure, potentially indicating a protective effect.
Q4: When is odds ratio used instead of relative risk?
A: Odds ratio is typically used in case-control studies where relative risk cannot be directly calculated, while relative risk is used in cohort studies.
Q5: What are the limitations of odds ratio?
A: OR can overestimate relative risk when outcomes are common (>10%). It may be less intuitive to interpret than relative risk for some audiences.