An odds ratio (OR) is a statistical measure that quantifies the strength of the association between two events, A and B. It is a ratio of two sets of odds: the odds of the event occurring in one group to the odds of it occurring in another group. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure. The odds ratio is commonly used in survey research, epidemiology, and to express the results of some clinical trials, such as in case-control studies.
Some important points to keep in mind about odds ratios are:
- The odds ratio is always positive and ranges from zero to very large.
- An odds ratio greater than 1 indicates an increased occurrence of an event, while an odds ratio less than 1 indicates a decreased occurrence of an event (protective exposure) .
- The confidence interval (CI) and p-value should be considered to determine the statistical significance of the odds ratio.
In summary, an odds ratio is a measure of association between two events that helps identify how likely an exposure is to lead to a specific event. It is commonly used in medical and social science research to express the results of case-control studies and other types of studies where the incidence of the outcome is not known.
