In what situation, Odd Ratio and Relative Risk can be equal? I was asked this question a few days ago. I googled it but couldn't find any answer. Any help is highly appreciated
If there's absolutely no difference between the groups in the probability of an outcome, then both the OR and the RR are 1.0. That's the only situation in which they can be exactly equal. This can be demonstrated algebraically; set the RR= p1/p2 equal to the OR= (p1/(1-p1))/(p2/(1-p2)) and reduce both sides; you get p1=p2.
Burke's answer is perfectly correct. The epidemiologists may be more flexible with the so called * rare desease assumption*. In the case p1 and p2 are low (the lower, the better) 1-p is close to 1 and RR close to OR - but closeness is not equality ...
It is considered that acceptable to say that if the events are low (
if the case-control study sampled from a dynamic population, then the odds ratio is a perfect estimation of the rate ratio(relative risk)?
i mean if disease which you are studying is rare disease, there is a OR=RR. it refers a concept that is rare disease assumption. https://en.wikipedia.org/wiki/Rare_disease_assumption
Yeap, in rare diseases, you can have the same value of both RR and OR.
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