Power analysis for odds ratio

If you have 2 different groups and you are going to determine how many times a risk factor will increase the risk (for the Odds ratio), you can estimate the minimum number of participants required in each group using the ratios you determined from the literature.

Required information

α error: shows the significance level of the p value. Choose between 0.05 and 0.01.

Strength (1-β): Select between 80% and 90% for targeted strength  

Expected rate in group I:

Expected rate in group II:

Sample calculation: When one of the expected rates in two groups is 20% and the other is 40% (OR=3), the information should be entered into the application as follows to calculate the minimum number of participants required in each group to find a significant difference between the groups at the 0.05 level and with 80% power.