Final answer:
The two common factors used in assessing risks are incidence, which tracks new cases of a disease, and prevalence, which includes all cases. These factors help calculate key epidemiological measures such as risk ratio and risk difference.
Step-by-step explanation:
When assessing risks, particularly in the context of epidemiology, the two common factors used are incidence and prevalence. Incidence refers to the number of new cases of a disease or health event in a population during a specific time period and is critical for understanding the risk factors associated with the health event, as well as concerns for disease spread. Prevalence, on the other hand, includes both new and existing cases in a population over a period of time, providing an overview of the overall health of the population.
Risk ratios and risk differences are important statistical measures derived from these factors. The risk ratio (or relative risk) indicates the strength of the association between a factor (like smoking) and a health outcome (like cardiovascular disease). This is calculated by dividing the incidence in the exposed group by the incidence in the unexposed group. The risk difference, determined by subtraction, measures the public health impact of eliminating a risk factor.