In medicine, odds ratio formula is the measure of odds of association between exposures divided by the odds of the outcomes (odds ratio = (ad/bc)). The formula is used to measure the strength of absence or presence of a property in a given population.
The odds ratio is computed in three steps. First, one has to compute the odds that an individual that has "B" also has "A." After this step, the odds that a given individual that does not have "B" also has "A" has to be calculated. Odds from the first step are then divided by the odds from the second step to calculate the odds ratio. The "A" and "B" represent certain properties such as high blood pressure and moderate alcohol consumption.