Epidemiology Concepts and Research Methods
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Questions and Answers

Which doctor will correctly identify more patients with colorectal cancer?

  • Dr.A
  • Neither will identify any patients
  • Both will correctly identify the same number
  • Dr.B (correct)

    • Which factor will not bias the results of a non-randomized study on mammographic screening?

  • Confounding by socioeconomic status
  • Lead time bias
  • Selection bias
  • Use of random sampling methods (correct)

    • What is the primary effect of primary prevention?

  • Extending the duration of the disease
  • Increasing the incidence of a disease
  • Preventing the occurrence of a disease (correct)
  • Reducing the mortality rate of a disease

    • What is a disadvantage of Mendelian randomization studies?

    <p>They require identifying specific gene variants</p> Signup and view all the answers

    In the pneumonia vaccination study, how many pneumonia cases were detected among nonrecipients in the intervention community?

    <p>48</p> Signup and view all the answers

    Which of the following groups is at a higher risk for selection bias in a screening study?

    <p>Low-income individuals who may avoid screening</p> Signup and view all the answers

    What is one limitation of using Mendelian randomization studies?

    <p>They require complex genetic data</p> Signup and view all the answers

    How many children received the pneumonia vaccine in the study?

    <p>394</p> Signup and view all the answers

    Which of the following frequency measures of HIV infection can be calculated at the end of the study?

    <p>All of the above</p> Signup and view all the answers

    What is the best estimate of the prevalence of a nonfatal disease with an incidence rate of 500/100,000 person-years?

    <p>333/100,000 person-years</p> Signup and view all the answers

    What best reflects the purpose of conducting a systematic review?

    <p>It employs explicit systematic methods to make decisions</p> Signup and view all the answers

    Which statement is a key advantage of case-crossover studies?

    <p>All of the above</p> Signup and view all the answers

    What does triangulation refer to in research methodology?

    <p>Compiling evidence from varied studies supporting a causal link</p> Signup and view all the answers

    Which of the following correctly describes a case-crossover design?

    <p>Uses the same participants over different time periods</p> Signup and view all the answers

    Which statement about systematic reviews is incorrect?

    <p>They are less comprehensive than meta-analyses</p> Signup and view all the answers

    In the context of the study of HIV infection, which option is least applicable?

    <p>Measuring daily incidence rates</p> Signup and view all the answers

    What is the simple indirect protective effectiveness of the pneumonia vaccine?

    <p>57%</p> Signup and view all the answers

    In a population of 1,000,000 in Cyprus with 1% having primary angle closure glaucoma, how many true positive cases will the test miss?

    <p>1,000</p> Signup and view all the answers

    Which statement about test characteristics is correct?

    <p>The positive predictive value varies with the prevalence of disease in the population being tested.</p> Signup and view all the answers

    In a study testing horses for a virus, what percentage of horses that test positive would be expected to be false positives?

    <p>87%</p> Signup and view all the answers

    How many false negatives were found in the new test for primary angle closure glaucoma?

    <p>100</p> Signup and view all the answers

    Considering the testing situation in Cyprus, what is the total number of confirmed cases of PACG in the population?

    <p>10,000</p> Signup and view all the answers

    When applying a new test to 200 horses, how many horses were found to harbor the virus?

    <p>40</p> Signup and view all the answers

    In a group of cattle, how many positives were identified using a perfect test?

    <p>5</p> Signup and view all the answers

    What is the denominator used to calculate the probability of illness among students during the varicella outbreak?

    <p>Number of susceptible students at the beginning of the period</p> Signup and view all the answers

    In the context of the Tylenol versus placebo trial, which explanation best accounts for Group A's better performance?

    <p>Tylenol might have had lingering effects due to insufficient washout</p> Signup and view all the answers

    What implications does the difference in non-adherence rates have for the fish oil memory trial?

    <p>It may lead to an underestimate of the treatment effect due to differential adherence.</p> Signup and view all the answers

    Which problem is least likely to be avoided in a small, randomized, double-blind study?

    <p>Loss to follow-up</p> Signup and view all the answers

    If a study shows a prolonged outbreak of varicella, which factor is crucial for assessing the risk among students?

    <p>The number of susceptible students at the start</p> Signup and view all the answers

    In the context of randomized trials, what is a potential issue with having differing adherence rates?

    <p>It may impact the validity of the outcomes.</p> Signup and view all the answers

    What is a likely reason for researchers to be surprised by the outcomes in the Tylenol trial?

    <p>They did not anticipate a placebo effect.</p> Signup and view all the answers

    Which factor can help mitigate biased estimates of disease outcome in a clinical trial?

    <p>Randomization of participants</p> Signup and view all the answers

    What is the sensitivity of the test being used?

    <p>99.5%</p> Signup and view all the answers

    What does a vaccine efficacy of 80% imply?

    <p>In a vaccinated population, 80% fewer people will contract the disease</p> Signup and view all the answers

    Which of the following statements is not true of a case-control study?

    <p>If rare disease assumption is violated, odds ratio remains valid</p> Signup and view all the answers

    What is the correct interpretation of an odds ratio of 1.53 from a case-control study of depression and suicidal behavior?

    <p>Odds of suicidal behavior are 1.53-fold higher in depressed individuals</p> Signup and view all the answers

    What is incorrect about randomization in a randomized controlled trial?

    <p>Outcomes will occur randomly and equally in both groups</p> Signup and view all the answers

    The concept of 'clinical equipoise' refers to which of the following?

    <p>State of genuine uncertainty about the best treatment</p> Signup and view all the answers

    In a case-control study, which factor is most crucial for validating the study's outcomes?

    <p>Matching of controls to cases on relevant factors</p> Signup and view all the answers

    What would be a limitation of a vaccine with 80% efficacy?

    <p>May result in some vaccinated individuals still contracting the disease</p> Signup and view all the answers

    In non-differential misclassification of exposure status, what is the expected direction of bias in the measure of association?

    <p>Towards the null</p> Signup and view all the answers

    What is a primary concern raised by the Canadian Cancer Society about the new drug for breast cancer?

    <p>Initial studies had methodological limitations.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a confounder?

    <p>It is on the causal pathway between exposure and outcome</p> Signup and view all the answers

    What ethical concerns does the oncologist face regarding enrolling patients in the randomized controlled trial?

    <p>Patients may receive a placebo instead of the new drug.</p> Signup and view all the answers

    What is the implication of the American Cancer Society’s position on the new drug for breast cancer?

    <p>They assert the results are conclusive and recommend the drug.</p> Signup and view all the answers

    Which of the following scenarios exemplifies selection bias?

    <p>Patients with severe symptoms are more likely to participate in a study.</p> Signup and view all the answers

    What would be an appropriate next step following the initial trials of the new breast cancer drug?

    <p>Conduct further studies to gather more evidence.</p> Signup and view all the answers

    What might be a consequence of misclassification bias in a study?

    <p>Distorted association between exposure and outcome.</p> Signup and view all the answers

    Study Notes

    2G03 Final Exam Practice Questions

    • Question 1: In a school experiencing a varicella outbreak from September to December, to calculate the risk of illness, use the number of susceptible students at the beginning of the period (September).

    • Question 2: A trial (n=20,654) comparing Tylenol and a placebo for muscle pain showed the Tylenol group (Group A) outperforming the placebo group (Group B). The most likely explanation is that Group B participants might've improved less due to knowing they were on the placebo group, or adequate randomization wasn't performed, or there wasn't a sufficient washout period between treatments.

    • Question 3: In a fish oil memory trial, 19% of the fish oil group and 3% of the placebo group forgot to take their supplements daily. This is not necessarily a problem as the non-adherence rate in the placebo group is comparatively smaller.

    • Question 4: In a small randomized, double-blind study, biased estimates of the disease outcome would be the most avoided problem.

    • Question 5: In a study of 100 injection drug users followed for two years, cumulative incidence and incidence rate can be calculated.

    • Question 6: The incidence rate of a nonfatal disease is 500 per 100,000 person-years, and the disease duration is 3 years. The prevalence estimate is 1500 per 100,000 person-years.

    • Question 7: The purpose of a systematic review is to use existing research evidence based on explicit systematic methods to guide decisions.

    • Question 8: Advantages of case-crossover studies include requiring fewer participants than traditional cohort designs, using participants as their own controls, and being less prone to confounding bias due to this self-control characteristic.

    • Question 9: Triangulation refers to compiling evidence from different methods (supporting a causal relationship)

    • Question 10: Dr. A's standard test, with sensitivity 90% and specificity 96%, is less accurate than Dr B's new test, with sensitivity and specificity both of 96%.

    • Question 11: A non-randomized mammographic screening study for breast cancer would not be biased by a selection bias based on the health status of participants.

    • Question 12: Primary prevention impacts the incidence rate of a disease, not mortality rate or duration.

    • Question 13: A disadvantage of Mendelian randomization studies is that the results can be equally confounded as observational studies, that they focus on selective outcomes, and that most exposures can't be studied due to limited genetic variants.

    • Question 14: The estimated simple indirect protective effectiveness of a pneumonia vaccine is 41% among children.

    • Question 15: In a glaucoma diagnosis test, the new test accurately diagnosed 900 patients as PACG and correctly labelled 950 as non-PACG. The test correctly diagnosed 900 out of 1000 patients, so the test correctly labelled PACG as having the disease in all the cases.

    • Question 16: A highly specific test is best for ruling out disease.

    • Question 17: In screening for virus infection in horses, 40 out of 60 positive test cases were actually positive using the gold standard. The test return 10 false positive tests out of 140 negatives. This translates to approximately 66.6% chances of a false positive diagnosis in the screening procedure.

    • Question 18: In a cattle population of 1000 with 5 positive cases for a specific disease, the test sensitivity is 0.5%.

    • Question 19: In a vaccinated population with an efficacy of 80%, 80% fewer people will contract the disease.

    • Question 20: A case-control study is not good at calculating the prevalence unless the rare disease assumption is satisfied.

    • Question 21: In a case control study with an odds ratio of 1.53 comparing depression and persistent suicidal behaviour, the odds of persistent suicidal behaviour are 1.53 times higher in people with depression than in people without depression.

    • Question 22: Incorrect statement about randomized controlled trials is that outcomes will occur at random and with equal frequency in both groups.

    • Question 23: Clinical equipoise refers to the assessment that no intervention is better than another.

    • Question 24: The most important reason for blinding in randomized controlled trials is to avoid subjective interpretations and perceptions of participants affecting the reporting and recording of trial outcomes.

    • Question 25: A planned crossover trial is more efficient than a parallel trial because participants act as their own controls, thus reducing variability and needing fewer subjects.

    • Question 26: A case-control study can be undermined by selection bias.

    • Question 27: Assuming no bias, if 8 vegetarians and 20 non-vegetarians developed heart disease in a 30-year follow-up study, the conclusion is that vegetarians were 20% less likely to develop the disease than non-vegetarians.

    • Question 28: An "intent-to-treat" analysis in a randomized controlled trial means that participants are analyzed based on the group they were originally assigned to, regardless of whether they adhered to the treatment or not.

    • Question 29: A planned crossover trial design is an effective and efficient means of assessing therapies for curing diseases.

    • Question 30: In a retirement party cheese-dip poisoning event, the attack rate for those eating cheese is 0.20. This means that for every 20 people who consume the cheese, one would contract food poisoning.

    • Question 31: False statement about volunteer bias is that it leads to underestimation of a screening program's effectiveness.

    • Question 32: The difference between random and systematic errors concerning a study is that random error is less of a problem in a large study while systematic error can never result in an underestimation of the true effect.

    • Question 33: In a large-scale study enrolling women and men about oral contraceptives, the bias that comes to play is selection bias.

    • Question 34: Non-differential misclassification of exposure status biases associations towards the null (no association).

    • Question 35: It's ethically acceptable to enroll patients in a randomized controlled trial for breast cancer, even with uncertainty about the drug's effectiveness, as it is expected that patients would be assigned to the experimental group (receiving the drug).

    • Question 36: A confounder is not a consequence of the exposure.

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    Description

    This quiz covers essential concepts in epidemiology and research methods, including biases in studies, advantages of different study designs, and prevalence estimates. Test your knowledge on screening studies, primary prevention effects, and systematic reviews in public health.

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