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Quizzes > Health & Medicine

Epi Quiz: Test Your Epidemiology Knowledge

Quick, free epidemiology quiz to check your skills. Instant results.

Editorial: Review CompletedCreated By: Techy JeeshanUpdated Aug 25, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
paper art epidemiology quiz with charts graphs risk ASHD rates magnifying glass test tube on coral background

This epi quiz helps you practice core epidemiology ideas, from risk measures to reading simple curves, and spot what to review next. Use it for a quick check or class prep, then try epidemiology practice questions, sharpen numbers with the biostatistics quiz, and explore public health trivia questions.

What measure reflects the proportion of a population that has a disease at a specific time point?
Mortality rate
Incidence
Attack rate
Prevalence
Prevalence is the proportion of individuals in a population who have a disease at a given time. It differs from incidence, which measures new cases over a period. Prevalence is influenced by both incidence and disease duration. .
Which study design starts by identifying individuals with and without a disease and looks back to assess exposure?
Case - control study
Cohort study
Cross-sectional study
Randomized controlled trial
A case - control study identifies cases with the disease and controls without it, and then looks back retrospectively at exposures. It is efficient for rare diseases or diseases with long latency. However, it can be susceptible to recall bias. .
How is cumulative incidence calculated?
Existing cases divided by total population
Death count divided by population
Person-time at risk divided by new cases
New cases divided by population at risk over a period
Cumulative incidence equals the number of new cases during a period divided by the population at start at risk. It measures risk of developing disease over that period. It assumes a closed population without losses. .
What does a risk ratio (relative risk) of 1.0 indicate?
No association between exposure and disease
Exposure increases risk
Exposure decreases risk
Study is invalid
A risk ratio of 1.0 means the risk in exposed is the same as in unexposed, indicating no association. Values above 1 suggest increased risk; below 1 suggest protective effect. Interpretation depends on confidence intervals too. .
Which of the following best defines incidence?
Total cases at a point in time divided by population
Prevalence of chronic disease
Number of new cases over a period divided by the at-risk population
Mortality count divided by population
Incidence measures new occurrences of disease and is calculated by dividing new cases by the population at risk during a specified period. It provides information on the risk of developing the disease. It is key for studying etiology. .
What term describes the accuracy of a test in correctly identifying those without the disease?
Sensitivity
Predictive value positive
Likelihood ratio
Specificity
Specificity is the ability of a test to correctly identify true negatives. High specificity means few false positives. It's critical when false positives carry high costs. .
Which term refers to the proportion of true positives among all who test positive?
Specificity
Sensitivity
Positive predictive value
Negative predictive value
Positive predictive value (PPV) is the proportion of true positives among those who test positive. It depends on the prevalence of disease in the population. Higher prevalence increases PPV. .
An outbreak lasting longer than expected baseline in a population is called:
Pandemic
Epidemic
Hyperendemic
Endemic
An epidemic is an increase in disease occurrence above normal expectancy in a population. Endemic refers to constant presence at baseline levels. A pandemic is a widespread epidemic over multiple countries or continents. .
Which measure is most useful for studying rare diseases?
Cohort study
Cross-sectional study
Case - control study
Randomized trial
Case - control studies are efficient for rare diseases because they start with cases and do not require following large cohorts. They can study multiple exposures. However, they may be prone to recall bias. .
Which bias arises when healthier individuals are more likely to be employed and included in certain studies?
Information bias
Selection bias
Confounding
Observer bias
The healthy worker effect is a type of selection bias where employed populations are generally healthier than the general population. This can underestimate risk in occupational studies. Recognizing it is crucial for correct interpretation. .
Which term refers to distortion of an association by a third variable?
Confounding
Bias
Effect modification
Interaction
Confounding occurs when a third variable is associated with both exposure and outcome, distorting their true relation. Controlling via stratification or multivariate analysis helps. It must be considered in study design and analysis. .
What is the case-fatality rate?
Deaths among diagnosed cases over a period
Recovered cases divided by total cases
Deaths among all individuals in population
New cases over time
Case-fatality rate is the proportion of individuals diagnosed with a disease who die from it in a specified period. It reflects disease severity. It's useful during outbreaks to gauge lethality. .
Which term defines an increase above the expected number of cases for a time and place?
Sporadic
Endemic
Pandemic
Epidemic
An epidemic occurs when disease incidence exceeds the expected baseline in a community over time. Endemic is the constant presence at baseline levels. Sporadic refers to irregular, unpredictable cases. .
Which measure accounts for both person number and time at risk?
Incidence rate (person-time)
Cumulative incidence
Proportionate mortality ratio
Prevalence
Incidence rate (person-time) divides new cases by total person-time at risk. It accounts for varying follow-up durations. It's particularly useful in dynamic populations. .
Which study design measures exposure and outcome at a single point in time?
Cohort study
Cross-sectional study
Case - control study
Randomized trial
Cross-sectional studies assess both exposure and outcome simultaneously in a population. They provide prevalence data but cannot establish temporality. They're useful for hypothesis generation. .
What does ASHD stand for in epidemiology of heart diseases?
Arrhythmic Stroke Heart Dysfunction
Autoimmune Heart Damage
Acute Septic Heart Disorder
Atherosclerotic Heart Disease
ASHD stands for Atherosclerotic Heart Disease, referring to narrowing of arteries due to plaque. It's a leading cause of morbidity and mortality globally. Rates of ASHD are important surveillance measures. .
What measure quantifies the proportion of disease in exposed attributable to that exposure?
Risk difference
Attributable fraction among the exposed
Population attributable risk
Odds ratio
Attributable fraction among the exposed (AF_e) is the proportion of disease in the exposed group due to the exposure itself. Calculated as (RR-1)/RR. It helps quantify impact of removing exposure. .
Which method of age adjustment uses a standard population distribution applied to study rates?
Indirect standardization
Regression adjustment
Direct standardization
Stratification
Direct standardization applies age-specific rates from the study population to a standard age distribution. It yields standardized rates comparable across populations. It requires precise age-specific data. .
In a cohort study, loss to follow-up most directly affects:
Specificity of disease
Measurement of exposure
Internal validity through selection bias
Sample size calculation
Loss to follow-up can introduce selection bias and affect internal validity if losses differ by exposure or outcome. It reduces statistical power and may distort effect estimates. Strategies include retention efforts and sensitivity analyses. .
What does an odds ratio approximate when the disease is rare?
Risk difference
Prevalence ratio
Relative risk
Attributable risk
When the outcome is rare (<10%), the odds ratio approximates the relative risk because odds and risk converge. This is known as the rare disease assumption. Researchers often use ORs from case - control studies as surrogates for RRs. .
Secondary attack rate is best defined as:
New cases among total population
Ratio of primary to secondary cases
Attack rate among initial cases
New cases among susceptible contacts of primary cases
Secondary attack rate measures spread in a closed group, calculated by dividing new cases among susceptible contacts by total susceptible contacts. It highlights transmissibility in households or schools. Useful during outbreak investigations. .
Which surveillance is ongoing, systematic collection, analysis, and interpretation of health data?
Passive surveillance
Continuous surveillance
Active surveillance
Sentinel surveillance
Continuous surveillance (often called routine or ongoing surveillance) involves systematic, uninterrupted data collection and analysis. Passive and active are modes of data gathering; sentinel uses selected sites. Continuous systems track disease trends over time. .
Population attributable risk percent (PAR%) indicates:
Difference in risk between exposed and unexposed
Proportion of cases in exposed due to exposure
Odds ratio minus one
Proportion of incidence in total population due to exposure
PAR% quantifies the proportion of all cases in a population attributable to an exposure. Calculated as (Pe(RR-1))/(1+Pe(RR-1)). It informs public health impact if exposure eliminated. .
Which is a primary prevention strategy in epidemiology?
Screening mammography
Childhood immunization
Administration of antibiotics to treat active TB
Rehabilitation after stroke
Primary prevention aims to prevent disease before it occurs. Childhood immunizations build immunity and prevent infectious diseases. Secondary prevention is early detection, tertiary is reducing impact of established disease. .
Which rate is age-adjusted using indirect standardization?
Crude rate
Directly age-adjusted rate
Standardized Mortality Ratio (SMR)
Person-time incidence rate
The standardized mortality ratio is the ratio of observed to expected deaths, using age-specific rates from a standard population. It's an indirect method when age-specific rates in the study population are unstable. SMR helps compare mortality across populations. .
Which analysis assesses the impact of changes in assumptions on study results?
Sensitivity analysis
Subgroup analysis
Confounder analysis
Meta-analysis
Sensitivity analysis tests robustness of results by varying key assumptions or parameters. It can identify how dependent findings are on certain inputs. Common in modeling and meta-analyses. .
What is the main limitation of ecological studies?
Ecological fallacy
High cost
Long follow-up needed
No exposure data
Ecological fallacy arises when associations at the group level are incorrectly inferred to individuals. Ecological studies use aggregated data and are hypothesis-generating. They cannot control for individual-level confounders. .
Which term describes the proportion of a disease occurrence in exposed minus the proportion in unexposed?
Attributable risk
Odds ratio
Risk ratio
Hazard ratio
Attributable risk (risk difference) is the difference in incidence between exposed and unexposed groups. It represents excess risk due to exposure. Useful for public health planning. .
Which measure uses the ratio of true positive rate to false positive rate for a diagnostic test?
Likelihood ratio
Odds ratio
Negative predictive value
Positive predictive value
Likelihood ratio for a positive test is sensitivity/(1 - specificity). It indicates how much a positive result increases the odds of disease. LR >10 provide strong evidence to rule in disease. .
Which regression model is appropriate for time-to-event analysis?
Poisson regression
Logistic regression
Linear regression
Cox proportional hazards model
The Cox proportional hazards model analyzes the effect of covariates on time-to-event data without specifying the baseline hazard. It yields hazard ratios estimating relative risk over time. It assumes proportional hazards across groups. .
What does the term 'effect modification' describe?
Bias due to loss to follow-up
Confounding by a third variable
Measurement error in exposure
Interaction where the effect of exposure differs by levels of another variable
Effect modification occurs when the magnitude or direction of an exposure - outcome association differs across strata of a third variable. It's important to report rather than control for in analysis. It provides etiological insights. .
Which analytical method assesses the probability of disease given a test result and prior probability?
Frequentist inference
Kaplan-Meier estimation
Meta-analysis
Bayesian updating
Bayesian updating combines prior probability with the likelihood from test data to compute a posterior probability. It's widely used in diagnostic test interpretation and decision-making. It requires specification of priors. .
In Poisson regression for count data, the link function is usually:
Log link
Logit link
Identity link
Probit link
Poisson regression typically uses a log link function to relate the expected log count to covariates. This ensures predicted counts are positive. It models incidence rates when including an offset. .
Which bias arises when exposure influences detection of disease differently between groups?
Information bias
Selection bias
Observer bias
Detection bias
Detection bias occurs when exposed and unexposed groups are monitored differently, leading to differential diagnosis rates. It can exaggerate or attenuate associations. Blinding and standardized protocols mitigate it. .
What does an ROC curve plot?
Sensitivity vs specificity
Positive predictive value vs prevalence
Likelihood ratio vs threshold
True positive rate vs false positive rate
An ROC curve plots sensitivity (true positive rate) against 1 - specificity (false positive rate) for various test thresholds. The area under the curve (AUC) quantifies test discrimination. Higher AUC indicates better diagnostic accuracy. .
Which phenomenon refers to systematic error in classification of exposure or outcome?
Observer bias
Misclassification bias
Selection bias
Confounding
Misclassification bias occurs when subjects are placed into incorrect exposure or outcome categories. It can be differential or nondifferential, affecting estimates differently. Validation studies and accurate measurement reduce it. .
In a meta-analysis, which statistic quantifies heterogeneity across studies?
Chi-square test of association
t-test
Q statistic and I²
F-test
The Q statistic tests for heterogeneity, and I² quantifies the proportion of variability due to heterogeneity rather than chance. High I² (>50%) indicates substantial heterogeneity. This informs choice between fixed- or random-effects models. .
What is the main assumption of the Cox proportional hazards model?
Normal distribution of survival times
Log-linearity of covariates
Proportional hazards ratio over time
Independent censoring only at study end
The Cox model assumes that hazard ratios between groups remain constant over time (proportional hazards). Violations can be checked via Schoenfeld residuals. If violated, time-dependent covariates may be used. .
Which term describes the difference between observed and expected events in a Poisson model?
Likelihood
Offset
Coefficient
Residual
In Poisson regression, residuals are the differences between observed and expected counts for each observation. They help detect model misfit. Types include deviance and Pearson residuals. .
Which study design can best establish causality?
Randomized controlled trial
Cross-sectional study
Case - control study
Cohort study
Randomized controlled trials minimize bias through random allocation and control groups, providing the strongest evidence for causality. They allow direct measurement of incidence and control over exposure. They may not always be ethical or feasible. .
Which tool is used to display survival probabilities over time?
Forest plot
ROC curve
Funnel plot
Kaplan - Meier curve
Kaplan - Meier curves estimate survival probabilities at different times accounting for censored data. They visually compare survival between groups. The log-rank test compares curves statistically. .
Which concept refers to the proportion of a population tested who truly have the disease?
Positive predictive value
Negative predictive value
Likelihood ratio
Specificity
Positive predictive value is the proportion of positive test results that are true positives. It depends on disease prevalence. High PPV means a positive result is likely correct. .
In cluster randomized trials, the unit of randomization is:
Outcome event
Geographic area or group
Time period
Individual participant
Cluster trials randomize groups or clusters (e.g., schools, clinics) rather than individuals. This design avoids contamination but requires adjustment for intracluster correlation. Sample size calculations incorporate clustering effects. .
What does the term 'ecological fallacy' warn against?
Overadjusting in regression
Mixing cohort and case - control data
Attributing group-level associations to individuals
Using uncontrolled confounders
Ecological fallacy occurs when relationships observed for groups are assumed to hold for individuals. It arises in ecological studies using aggregated data. Avoid by using individual-level data when possible. .
What does Mendelian randomization use to infer causality in epidemiology?
Genetic variants as instrumental variables
Ecological correlations
Random assignment of subjects
Blinding in trials
Mendelian randomization uses genetic variants associated with an exposure as instruments to estimate causal effects on outcomes, minimizing confounding. It relies on random allocation of alleles at conception. It assumes no pleiotropy or linkage disequilibrium biases. .
In spatial epidemiology, which method detects disease clusters?
SaTScan (spatial scan statistics)
Meta-analysis
Logistic regression
Kaplan - Meier analysis
SaTScan uses spatial scan statistics to identify clusters by comparing observed and expected cases within moving windows. It adjusts for multiple testing and population density. Widely used for outbreak detection. .
Which model extends the Cox model to allow time-varying covariates?
Stratified Cox model
Time-dependent Cox model
Weibull regression
Accelerated failure time model
The time-dependent Cox model includes covariates that change over time, allowing hazard ratios to vary with exposure history. It requires appropriate data structure and coding of time intervals. Useful in chronic disease studies. .
In Poisson regression for rare events, the use of an offset term adjusts for:
Confounding
Interaction effects
Overdispersion
Time at risk or population size
An offset term, often log person-time or log population, adjusts the model for differing exposure times or population sizes. It ensures rate interpretation of coefficients. Essential in incidence rate modeling. .
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Study Outcomes

  1. Understand ASHD rates -

    Calculate and interpret incidence and prevalence measures of arteriosclerotic heart disease to differentiate between rate-based and proportion-based metrics.

  2. Calculate relative risk -

    Use data from cohort scenarios to compute relative risk values and assess the strength of associations between exposures and health outcomes.

  3. Compute odds ratios -

    Derive and interpret odds ratios from case - control data sets to quantify the relationship between exposures and diseases.

  4. Identify epi quiz concepts -

    Recognize and explain fundamental epidemiologic principles presented in the epi.tests quiz to enhance comprehension and retention.

  5. Differentiate study measures -

    Compare and contrast relative risk, odds ratios, and ASHD rates to determine the appropriate application of each measure in epidemiologic studies.

  6. Apply teacher epi assessment sample questions -

    Engage with teacher epi assessment sample questions to simulate real-world testing scenarios and reinforce core epidemiology skills.

Cheat Sheet

  1. Relative Risk (RR) Calculation -

    Use the cohort formula RR = [a/(a+b)] ÷ [c/(c+d)] to compare incidence in exposed versus unexposed groups. For example, if 30 of 100 exposed and 10 of 100 unexposed develop the disease, RR = 0.3/0.1 = 3.0, indicating a threefold higher risk (CDC, 2022).

  2. Odds Ratio (OR) Interpretation -

    In case - control studies, compute OR = (a×d) ÷ (b×c) from a 2×2 table to estimate exposure odds among cases versus controls. An OR >1 suggests a positive association; for instance, OR = 2.5 means cases had 2.5 times the odds of exposure (J Epidemiol Res).

  3. Age-Standardized Heart Disease Rate (ASHD) -

    Apply the direct standardization method by weighting age-specific ASHD rates against a standard population (e.g., WHO world standard) to remove age-structure bias. This lets you compare regions fairly - simply multiply each age-specific rate by its standard population weight and sum the results (WHO, 2021).

  4. Sensitivity & Specificity -

    Recall Sensitivity = TP/(TP+FN) and Specificity = TN/(TN+FP), where TP/FN are true/false negatives. Use the mnemonics "SnOUT" (high Sensitivity rules OUT disease) and "SpIN" (high Specificity rules IN disease) for quick recall (Johns Hopkins Univ.).

  5. Maximizing epi.tests Practice -

    Leverage epi.tests quizzes and teacher epi assessment sample questions to identify epi quiz gaps by grouping flashcards on RR, OR, AR and study design. Pro tip: use the "FACES" mnemonic - Flashcards, Assess, Chart, Explain, Self-test - to boost retention and confidence before any epi quiz.

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