1. Relative risk estimates the extent of the association between an exposure and a disease. It estimates the likelihood of developing the disease in the exposed group as compared to the unexposed group.
  2. A relative risk = 1.0 indicates that the incidence rate of disease in the exposed group is equial to the incidence rate in the unexposed group. Therefore the data does not provide evidence for an association.
  3. A relative risk >1 indicates a positive association or an increased risk. This risk increases in strength as the magnitufe of the relative risk increases.
  4. A relative risk <1 indicates a negative association or decreased risk (possibly a protective effect) if the relative risk is between 0 and 1.0. Relative risk is not expressed in negative numbers.

See Relative Risk calculation taken from 2011 Training Handout - Potato Salad