The odds ratio ((a/c)/(b/d)) looks at the likelihood of an outcome in relation to a characteristic factor In epidemiological terms, the odds ratio is used as a point estimate of the relative risk in retrospective studies Odds ratio is the key statistic for most casecontrol studiesWith an odds ratio, the outcome can be the starting point with which we can determine the relative odds of someone having been exposed to a risk factor Alternatively, we can also use it to describe the ratio of disease odds given the exposure status Once we know the exposure and disease status of a research population, we can fill in their corresponding numbers in the following table To calculate the odds ratioWhen the disease is rare, the odds ratio will be a very good approximation of the relative risk The more common the disease, the larger is the gap between odds ratio and relative risk In our example above, p wine and p no_wine were 0009 and 0012 respectively, so the odds ratio was a good approximation of the relative risk OR = 0752 and RR = 075
Box 9 2 A Calculation Of Rr Or And Rd
