The Risk Ratio (RR) is a statistical measure used to compare the risk of a certain event occurring in two different groups. It is calculated by dividing the risk in the exposed group by the risk in the unexposed group. For example, if Group A has a 20% risk of developing a disease and Group B has a 10% risk, the risk ratio would be 2.0, indicating that Group A is twice as likely to develop the disease compared to Group B. Risk ratios are commonly used in epidemiology and clinical research to assess the strength of an association between an exposure and an outcome. An RR of 1 indicates no difference in risk between the groups, while an RR greater than 1 suggests increased risk, and an RR less than 1 indicates reduced risk. Understanding risk ratios helps researchers and healthcare professionals make informed decisions about prevention and treatment strategies.