HS300 Exam 2 Formulas UPDATED ACTUAL Questions and
CORRECT Answers
Prevalence Ration (PR) Prevalence of outcome in exposed group / prevalence of outcome in unexposed
group
Prevalence (exposed) Cases in exposed / total exposed population
Prevalence (unexposed) Cases in unexposed / total unexposed population
Relative Risk Formula incidence rate in exposed/incidence rate in non-exposed
Odds Ratio (OR) odds of disease in exposed / odds of disease in unexposed
Attributable Risk (AR) difference in risk between exposed and unexposed groups
AR% Formula (Total incidence - incidence in unexposed) / risk for exposed group x 100
Population Attributable Risk Percent Formula
Concurrent study an epidemiological design where researchers identify a group of participants
(cohort) at the start, classify them by exposure, and follow them forward in time
to observe who develops the outcome
Prospective study start in the present and study groups into the future
retrospective study look into the past for associations between suspected causative factors and
disease
Cross sectional study a study in which data are collected at only one time point, type of prevalence
study
Case control study A type of epidemiologic study where a group of individuals with the diseases,
referred to as cases, are compared to individuals without the disease, referred to
as controls
Ecological study a study in which the units of analysis are populations or groups of people rather
than individuals
CORRECT Answers
Prevalence Ration (PR) Prevalence of outcome in exposed group / prevalence of outcome in unexposed
group
Prevalence (exposed) Cases in exposed / total exposed population
Prevalence (unexposed) Cases in unexposed / total unexposed population
Relative Risk Formula incidence rate in exposed/incidence rate in non-exposed
Odds Ratio (OR) odds of disease in exposed / odds of disease in unexposed
Attributable Risk (AR) difference in risk between exposed and unexposed groups
AR% Formula (Total incidence - incidence in unexposed) / risk for exposed group x 100
Population Attributable Risk Percent Formula
Concurrent study an epidemiological design where researchers identify a group of participants
(cohort) at the start, classify them by exposure, and follow them forward in time
to observe who develops the outcome
Prospective study start in the present and study groups into the future
retrospective study look into the past for associations between suspected causative factors and
disease
Cross sectional study a study in which data are collected at only one time point, type of prevalence
study
Case control study A type of epidemiologic study where a group of individuals with the diseases,
referred to as cases, are compared to individuals without the disease, referred to
as controls
Ecological study a study in which the units of analysis are populations or groups of people rather
than individuals
