Odds Ratio Calculator


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)

Disease
No Disease
Exposed
Not Exposed
Confidence Level =

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 folllowing 2x2 crosstabulation:

 
  Disease  
No Disease
Exposed
\(a\)
\(b\)
Not Exposed
\(c\)
\(d\)

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:

\[OR = \frac{a/b}{c/d} \]



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