NR 503 — WEEK 8 ENHANCED EXAM STUDY GUIDE
Population Health, Epidemiology, Biostatistics & Health Policy
Original-material companion: This is an independently written study resource inspired by the publicly visible topics in the
referenced Stuvia preview. It is not a reproduction of the paid document.
SECTION I — EPIDEMIOLOGY & POPULATION HEALTH
Question: What is the epidemiologic triangle?
Answer: A framework describing disease causation through the interaction of the agent, host, and
environment. The model is useful for organizing prevention strategies because changing any component can
alter disease risk.
Question: Where does genetics fit in the epidemiologic triangle?
Answer: Genetic characteristics are generally considered a host factor. Host factors include age, sex,
immune status, genetic susceptibility, behaviors, and underlying conditions.
Question: What is the incubation period?
Answer: The time between exposure to an infectious agent and the appearance of the first signs or
symptoms. Incubation periods are important for surveillance, contact tracing, isolation decisions, and outbreak
investigation.
Question: What is prevalence?
Answer: The proportion of a population that has a condition at a specified time or during a specified period.
Prevalence is influenced by both incidence and the duration of disease.
Question: What is incidence?
Answer: The occurrence of new cases in a population at risk during a specified period. Incidence is
especially useful for studying risk and identifying factors associated with developing disease.
Question: What is the difference between incidence and prevalence?
Answer: Incidence counts new cases; prevalence counts existing cases. A disease can have high prevalence
even when incidence is modest if affected individuals live with the condition for a long time.
Question: What is primary prevention?
Answer: Action taken before disease occurs to prevent its onset. Examples include immunization, health
education, tobacco-use prevention, and environmental controls.
Question: What is secondary prevention?
Answer: Early detection and prompt intervention intended to identify disease at an early stage. Screening
programs are classic examples.
Question: What is tertiary prevention?
Answer: Intervention after disease is established to reduce complications, disability, progression, or loss of
function. Rehabilitation and chronic-disease management are examples.
, SECTION II — STUDY DESIGNS & MEASURES
Question: What is a cross-sectional study?
Answer: A study that measures exposure and outcome at a particular point or period in time. It is useful for
estimating prevalence but generally cannot establish temporal sequence between exposure and outcome.
Question: What is a cohort study?
Answer: A study in which groups are classified according to exposure and followed to compare outcome
occurrence. Cohort designs are well suited to calculating incidence and relative risk.
Question: What is a case-control study?
Answer: A study that begins with people who have the outcome (cases) and compares their prior exposures
with those of controls. It is particularly useful for rare diseases and often uses the odds ratio as the principal
association measure.
Question: What is an odds ratio?
Answer: A measure commonly used in case-control studies that compares the odds of exposure among
cases with the odds of exposure among controls. An OR above 1 suggests a positive association; an OR
below 1 suggests a negative association.
Question: What is relative risk?
Answer: The ratio of disease risk among an exposed group to disease risk among an unexposed group. RR =
1 indicates no association; values above 1 indicate increased risk; values below 1 indicate reduced risk.
Question: What is sensitivity?
Answer: The ability of a test to correctly identify people who truly have the disease. High sensitivity produces
few false negatives and is particularly valuable when missing disease would be consequential.
Question: What is specificity?
Answer: The ability of a test to correctly identify people who do not have the disease. High specificity
produces few false positives.
Question: What is positive predictive value?
Answer: The probability that a person actually has the disease given a positive test result. PPV is strongly
influenced by disease prevalence.
Question: What is negative predictive value?
Answer: The probability that a person truly does not have the disease given a negative test result. NPV also
varies with prevalence.
Population Health, Epidemiology, Biostatistics & Health Policy
Original-material companion: This is an independently written study resource inspired by the publicly visible topics in the
referenced Stuvia preview. It is not a reproduction of the paid document.
SECTION I — EPIDEMIOLOGY & POPULATION HEALTH
Question: What is the epidemiologic triangle?
Answer: A framework describing disease causation through the interaction of the agent, host, and
environment. The model is useful for organizing prevention strategies because changing any component can
alter disease risk.
Question: Where does genetics fit in the epidemiologic triangle?
Answer: Genetic characteristics are generally considered a host factor. Host factors include age, sex,
immune status, genetic susceptibility, behaviors, and underlying conditions.
Question: What is the incubation period?
Answer: The time between exposure to an infectious agent and the appearance of the first signs or
symptoms. Incubation periods are important for surveillance, contact tracing, isolation decisions, and outbreak
investigation.
Question: What is prevalence?
Answer: The proportion of a population that has a condition at a specified time or during a specified period.
Prevalence is influenced by both incidence and the duration of disease.
Question: What is incidence?
Answer: The occurrence of new cases in a population at risk during a specified period. Incidence is
especially useful for studying risk and identifying factors associated with developing disease.
Question: What is the difference between incidence and prevalence?
Answer: Incidence counts new cases; prevalence counts existing cases. A disease can have high prevalence
even when incidence is modest if affected individuals live with the condition for a long time.
Question: What is primary prevention?
Answer: Action taken before disease occurs to prevent its onset. Examples include immunization, health
education, tobacco-use prevention, and environmental controls.
Question: What is secondary prevention?
Answer: Early detection and prompt intervention intended to identify disease at an early stage. Screening
programs are classic examples.
Question: What is tertiary prevention?
Answer: Intervention after disease is established to reduce complications, disability, progression, or loss of
function. Rehabilitation and chronic-disease management are examples.
, SECTION II — STUDY DESIGNS & MEASURES
Question: What is a cross-sectional study?
Answer: A study that measures exposure and outcome at a particular point or period in time. It is useful for
estimating prevalence but generally cannot establish temporal sequence between exposure and outcome.
Question: What is a cohort study?
Answer: A study in which groups are classified according to exposure and followed to compare outcome
occurrence. Cohort designs are well suited to calculating incidence and relative risk.
Question: What is a case-control study?
Answer: A study that begins with people who have the outcome (cases) and compares their prior exposures
with those of controls. It is particularly useful for rare diseases and often uses the odds ratio as the principal
association measure.
Question: What is an odds ratio?
Answer: A measure commonly used in case-control studies that compares the odds of exposure among
cases with the odds of exposure among controls. An OR above 1 suggests a positive association; an OR
below 1 suggests a negative association.
Question: What is relative risk?
Answer: The ratio of disease risk among an exposed group to disease risk among an unexposed group. RR =
1 indicates no association; values above 1 indicate increased risk; values below 1 indicate reduced risk.
Question: What is sensitivity?
Answer: The ability of a test to correctly identify people who truly have the disease. High sensitivity produces
few false negatives and is particularly valuable when missing disease would be consequential.
Question: What is specificity?
Answer: The ability of a test to correctly identify people who do not have the disease. High specificity
produces few false positives.
Question: What is positive predictive value?
Answer: The probability that a person actually has the disease given a positive test result. PPV is strongly
influenced by disease prevalence.
Question: What is negative predictive value?
Answer: The probability that a person truly does not have the disease given a negative test result. NPV also
varies with prevalence.
