**Instructions:** This calculator computes the Odds Ratio (OR) for a 2x2 crosstabulation, which measures the ratio of the odds of exhibiting a condition (or disease) for those in an exposed group, versus the the odds of exhibiting the condition (or disease) for those in the non-exposed group. Please type the 2x2 table data and also indicate the confidence level required to compute the confidence interval for the odds ratio (OR)

## How Do You Calculate Odds Ratios?

**More about the Odds Ratio (OR)**

The odds ratio (OR) corresponds to ratio of the odds of having a condition for those exposed to a certain treatment, versus the the odds of having a condition for those not exposed to the treatment.

Let us consider the following 2x2 crosstabulation:

The Odds Ratio of having the condition for those in the exposed group respect to the non-exposed group is computed using the following formula:

\[OR = \frac{a/b}{c/d} \]Related to the concept of odds ratio, you may find useful to use our relative risk calculator.

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