Question

Under what conditions will large differences occur between calculations for the risk ratio and the odds ratio, made using the same study results?

Answer 1

Let's consider the following contingency table.

Then,

i.e. RR and OR will be almost same if b>>a and c>>d otherwise there will be large differences.

In other words if b and c are not largely different than a and d respectively, there will be large differences in RR and OR

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