The following is a 2 by 2 table used to compute the odds ratio. Enter the data in the cells for the appropriate rows and columns (green background), then click on the button labelled Calculate to compute the Odds Ratio and the corresponding values for the 95% confidence intervals.


Outcome of interest Present (Cases) Outcome of interest Absent (Controls)

Row 1 Column 1 Row 1 Column 2 Data Check (Numerator)
Suspected causal mechanism present
(Exposed)

Row 2 Column 1 Row 2 Column 2 Data Check (Denominator)
Suspected causal mechanism absent
(Not Exposed)
Odds Ratio =
(AD) / (BC)

Natural Log oddsRatio
 Standard Error of lnOR
 95%CI lnOR lower limit
 95%CI lnOR upper limit
Exponentiating the 95% Confidence Interval\'s Upper and Lower limits will return the estimated values to the original scale scores lower limit of 95%CI
Odds Ratio
upper limit of 95%CI
Odds Ratio


Given that the 95% confidence interval does not include 1 then we can say that there is a relationship between the suspected risk factor and the outcome.
1) If the computed odds ratio is greater than 1 then the researcher suggests that there is a positive relationship between the suspected cause and the outcome.
2) If the computed odds ratio is less than 1 then the researcher may suspect that the stimulus of interest is in fact demonstrating a protective effect on the sample observed.
3) If the computed odds ratio is close to 1 then the researcher concedes that there is no relationship between the suspected cause and the outcome. The term close is determined by the researcher based on evaluation of the confidence interval.