Section D: Relative Risk The Relative Risk measures the strength of the association that a risk factor or exposure has with an outcome. It is interpreted based on 1 representing no association. A relative risk that is greater than 1 indicates that the risk factor/exposure is positively associated with the outcome and may indicate a causal relationship. A relative risk that is less than 1 indicates that the risk factor/exposure is negatively associated with the outcome and may indicate a protective effect. A 2X2 table can be constructed to assist in calculating the relative risk: Risk Factor Present Risk Factor Absent Outcome (or Disease) Present Outcome (or Disease) Absent b d Exposure (Smoking during pregnancy) a The formula for Relative Risk (RR) is: Incidence of the disease (or outcome) with the risk factor present (exposed) Incidence of the disease (or outcome) with the risk factor absent (unexposed) Questions: 1. Use Table 4 to calculate the Relative Risk of low birth weight with smoking as the risk factor for the combined population of African American and White births. No Exposure (No smoking during pregnancy) Totals Disease (LBW) a/(a+b) c/(c+d) No disease (Normal BW) Totals 2. How would you interpret the Relative Risk of low birth weight with smoking as the risk factor?