Final answer:
To calculate relative risk, organize the data in a 2 x 2 contingency table, with the incidence of health events for both exposed and non-exposed groups. The risk ratio, more than one, signifies an increased risk with exposure, and it is useful for studies like cohort and case-control studies.
Step-by-step explanation:
To calculate the relative risk, you should set up the data in a 2 x 2 table, known as a contingency table. This table will typically display the incidence of a health event among two groups: those exposed to a variable and those not exposed. The relative risk is calculated by dividing the incidence of the outcome in the exposed group by the incidence in the non-exposed group. When the calculated risk ratio is more than one, it implies there is an increased risk associated with the exposure. Epidemiologists find this measurement particularly useful in cohort studies, but it can also be applied in case-control studies during disease outbreaks to track risk factors and assign potential causes.
The 2 x 2 table organizes the data into four sections: the number of exposed individuals with the outcome, the number of exposed without the outcome, the number of non-exposed with the outcome, and the number of non-exposed without the outcome. This setup of data supports the calculation of relative frequency and, therefore, the calculation of experimental probability.
For an applied example, if a food-borne disease outbreak occurred, epidemiologists would use this type of table, including the cases of illness among those who consumed a particular contaminated food item versus those who did not consume it, to determine which food was contaminated by calculating the relative risk for each food item.