Final answer:
Relative risk in the PRF Approach is calculated by organizing data into a 2 x 2 table and using the formula RR = incidence of outcome in exposed group / incidence of outcome in non-exposed group. The calculated relative risk for each food item helps determine which food might be contaminated by comparing these risk measures.
Step-by-step explanation:
The risk measure you mention appears to refer to the relative risk, which is commonly used in the fields of epidemiology and public health to measure the association between exposure to a certain factor and the occurrence of a specific outcome, such as a disease. To calculate relative risk in the second step of the Probability Risk Factor (PRF) Approach, we first need to find the incidence rates of the outcome for both the exposed and unexposed groups. This is generally done by organizing the data into a 2 x 2 table format. Relative risk is then calculated by dividing the incidence of the health event in the exposed group by the incidence in the unexposed group, using the formula: RR = incidence of outcome in exposed group / incidence of outcome in the non-exposed group.
To calculate the relative risk of each food item potentially being contaminated, you start by calculating the incidence for each group. For example, if you had a group of people who ate a certain food item and a group who did not, and you observed a health outcome in both groups, you would use these incidences in the formula to compute the relative risk for that particular food item.