Dear RG users,
I am wondering suggestions from colleagues; what is the clear boundary between OR and RR? How can I easily understand and interprate these epidemiological tools?
Reflections are appreciated,
Dear colleague, Odds are one category divided by the other and Risk Ratio of the probability that the outcome is present in one group, relative to the other. Odds of an event is the probability that it occurs divided by the probability that it does not occur. Odds ratio is the ratio of two odds.
In short
Risk = number experiencing event divided by number who could
Odds = number experiencing event divided by number who didn’t
Dear Awoke
Relative risk (RR) is a measure of strength between an exposure (say smoking) and an outcome (say lung cancer). It is calculated as the ratio of incidence rate of lung cancer among smokers to the incidence rate of lung cancer among non-smokers. As the value of the relative risk is higher the association is stronger and the aetiological implication is high. Odds ratio is an estimate of RR calculated in case-control studies. Risk difference (attributable risk) is the difference between the incidence rate among exposed and the incidence rate among the non-exposed. It gives an idea about the expected reduction in incidence rate if the exposure is eliminated. The attributable risk can be calculated in both cohort and case control studies.
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