Measures of Effect in Epidemiology
Exam Questions and Answers 100% Pass
Absolute risk - ANSWER-The incidence of disease.
Relative risk (or risk ratio; RR) - ANSWER-Expresses how much more likely an
exposed person is to get the disease in comparison to an unexposed person.
Attributable risk (or risk difference) - ANSWER-The difference in risk between
exposed and unexposed groups.
Attributable risk percentage - ANSWER-[(RR - 1)/RR] × 100%
Absolute risk reduction (ARR) - ANSWER-The difference in risk that is
attributable to the intervention compared to a control.
Number needed to treat (NNT) - ANSWER-Number of individuals who need to
be treated for one patient to benefit.
Odds ratio (OR) - ANSWER-An estimate of relative risk that is used in case-
control studies.
Hazard ratio (HR) - ANSWER-An estimate of the chances that an event occurs in
the treatment arm of a trial vs the nontreatment arm.
©️COPYRIGHT 2025, ALL RIGHTS RESERVED. 1
Exam Questions and Answers 100% Pass
Absolute risk - ANSWER-The incidence of disease.
Relative risk (or risk ratio; RR) - ANSWER-Expresses how much more likely an
exposed person is to get the disease in comparison to an unexposed person.
Attributable risk (or risk difference) - ANSWER-The difference in risk between
exposed and unexposed groups.
Attributable risk percentage - ANSWER-[(RR - 1)/RR] × 100%
Absolute risk reduction (ARR) - ANSWER-The difference in risk that is
attributable to the intervention compared to a control.
Number needed to treat (NNT) - ANSWER-Number of individuals who need to
be treated for one patient to benefit.
Odds ratio (OR) - ANSWER-An estimate of relative risk that is used in case-
control studies.
Hazard ratio (HR) - ANSWER-An estimate of the chances that an event occurs in
the treatment arm of a trial vs the nontreatment arm.
©️COPYRIGHT 2025, ALL RIGHTS RESERVED. 1
