-An odds ratio of more than 1.0 suggests a positive association between the exposure and disease or other outcome.
-An OR less than 1.0 indicates that the exposure might be a protective factor.
-When OR=1, there is no association between exposure and outcome.
-Population Risk Difference
RR=(Incidence rate in the exposed)/(Incidence rate in the nonexposed)
-A RR of 1.0 implies that the risk (rate) of disease among the exposed is not different from the risk of disease among the nonexposed.
-A RR >2.0 implies that the risk is more than twice as high among the exposed as among the nonexposed.
-If RR is sometimes called a protective effect.
AR=(Incidence rate in the exposed group)-(Incidence rate in the nonexposed group)
PRD=(Incidence in the total population)-(Incidence in the nonexposed segment)
Error that occurs when the relationship between exposure and disease is different for those who participate in a study versus those who would be theoretically eligible for the study but do not participate.
-People whose life expectancy are shortened by a disease are less likely to be employed than healthy persons.
Consequence would be a reduced (or attenuated) measure of effect (e.g., odds ratio or relative risk) for an exposure that increases morbidity or mortality.