Biostatistics and Epidemiology Step 1 Sample Questions Set 11. A study wishes to assess birth characteristics in a population. Which of the following variables describes theappropriate measurement scale or type?A. ContinuousB. OrdinalC. NominalD. Dichotomousa.b.c.d.Birthweight in gramsBirthweight classified as low, medium, highBirthweight classified as low, not lowDelivery type classified as cesarean, natural, induced2. In an experimental study, patients with advanced breastcancer are treated with a new drug. After three years offollow-up, radiographic scans are used to determine thenumber of metastatic lesions for each study patient. Thenumber of lung metastases for each subject is shown in thefigure. Based on these data, what is the average number ofmetastatic lung lesions for patients treated with the newdrug?a.b.c.d.e.Between 0 and 11Between 1 and 22Between 2 and 33. In a medical class of 147 students, the distribution of scores on a biochemistry final examination has a meanequal to 67, a median equal to 76, a mode equal to 80, a standard deviation equal to 5.5, and a variance equal to30.25. Three students were unable to take the test on the scheduled date and were given a different form of theexam 1 week later. Which parameter is most likely to be the least biased estimator of central tendency for thisdistribution of biochemistry test scores?a. Meanb. Medianc. Moded. Standard deviatione. Variance4. A large study of serum cholesterol levels in patients with diabetes mellitus reveals that the parameter isnormally distributed with a mean of 230 mg/dL and standard deviation of 10 mg/dL. According to these results,95% of serum cholesterol observations in these patients lie between which of the following limits?a. 220 and 240 mg/dLb. 225 and 235 mg/dLc. 210 and 250 mg/dLd. 200 and 260 mg/dLe. 220 and 260 mg/dL1

5. Which of the following graphs most closely corresponds to a correlation coefficient of 1?6. An investigator suspects that acetaminophen use during the first trimester of pregnancy can cause neural tubedefects. She estimates the risk of neural tube defect in the general population is 1:1,000. Which of the followingis the best study design to investigate the hypothesis?a. Cohort studyb. Case-control studyc. Clinical triald. Ecologic Studye. Cross-sectional study7. Officials at a large community hospital report an increased incidence of acute lymphocytic leukemia (ALL) amongchildren aged 5 – 12. They point out that some households in the community are exposed to chemical wastefrom a nearby factory. They believe that chemical waste causes leukemia. If a study is designed to evaluate thehospital officials’ claim, which of the following subjects are most likely to comprise the control group?a. Children exposed to the chemical waste who do not suffer from ALLb. Children not exposed to the chemical waste who do not suffer from ALLc. Children from the hospital’s outpatient clinic who do not suffer from ALLd. Children not exposed to the chemical waste who suffer from ALLe. Children who suffered from ALL but got cured8. 500 women aged 40 – 54 who present for routine check-ups are asked about their meat consumption. 20% ofthe women turn out to be vegetarian. During the ensuing 5 years, 5 vegetarians and 43 non-vegetarians developcolorectal cancer. Which of the following best describes the study design?a. Case series reportb. Cohort studyc. Case-control studyd. Cross-sectional studye. Randomized clinical trial9. A group of patients with lung cancer is matched to a group of patients without lung cancer. Their smoking habitsover the course of their lives are compared. On the basis of this information, researchers compute the odds ofsmoking among patients with lung cancer compared to the odds of smoking among those without lung cancer.This is an example of aa. Case-control studyb. Cohort studyc. Cross-sectional studyd. Longitudinal studye. Randomized controlled study2

10. In a study, a group of people are exposed to an environmental toxin but are not treated. Instead, they areobserved over time on a standard set of measures to ascertain the potential effects of the toxin. This type ofstudy design is calleda. Clinical trialb. Double-blindc. Longitudinald. Prospective cohorte. Retrospective cohort11. A new drug with in vitro activity against HIV is tested on a population of patients with Western-blot confirmedHIV infections. Out of the 200 individuals in the patient population, 100 are chosen by lottery to receive thedrug. The drug, which is tasteless, is administered in a cup of orange juice; the other patients receive pureorange juice. Neither the nurses, doctors, nor the patients know which patients receive the drug. At the end ofthe study period, the number of CD4 T cells is determined for all of the subjects. This is an example of aa. Case-control studyb. Case reportc. Cohort studyd. Cross-sectional studye. Double-blind randomized clinical trial12. A city has a population of 250,000. Of these, 10,000 have disease X, which is incurable. There are 1,000 newcases and 400 deaths each year from this disease. There are 2,500 deaths per year from all causes. Theprevalence of this disease is given bya. 400/250,000b. 600/250,000c. 1,000/250,000d. 2,500/250,000e. 10,000/250,00013. There were no new cases of Ebola virus in the United States from January 1, 1997 through January 1, 1998.Which of the following epidemiologic terms does this statement describe?a. Incidenceb. Lifetime expectancyc. Lifetime prevalenced. Period prevalencee. Point prevalence14. Based on the information in the 2 x 2 table below, which of the following expressions represents the prevalenceof disease?ExposedUnexposeda.b.c.d.e.Disease positiveWXW/(W X)[W/(W Y)]/[X/(X Z)](W/Y)/(X/Z)(W/X)/(Y/Z)(W X) /(W X Y Z)3Disease NegativeYZ

15. In a survey of 10,000 IV drug users in town A, 1,000 turn out to be infected with hepatitis. During one year offollow-up, 100 patients with hepatitis C infection die. Also during follow-up, 100 IV drug users acquire hepatitisC. Which of the following is the best estimate of the annual incidence of hepatitis C infection in IV drug users intown A?a. 1,000/10,000b. 1,100/10,000c. 100/10,000d. 100/9,000e. 100/9,80016. The following graph represents the vaccination rate dynamicsfor hepatitis B in IV drug users in town A. Which of thefollowing hepatitis B statistics is most likely to be affected bythe reported data?a.b.c.d.e.Hospitalization rateCase fatality rateMedian survivalIncidenceCure rate17. An observational study in diabetics assesses the role of an increased plasma fibrinogen level on the risk ofcardiac events. 130 diabetic patients are followed for 5 years to assess the development of acute coronarysyndrome. In the group of 60 patients with a normal baseline plasma fibrinogen level, 20 develop acutecoronary syndrome and 40 do not. In the group of 70 patients with a high baseline plasma fibrinogen level, 40develop acute coronary syndrome and 30 do not. Which of the following is the best estimate of relative risk inpatients with a high baseline plasma fibrinogen level compared to patients with a normal baseline plasmafibrinogen level?a. (40/30)/(20/40)b. (40*40)/(20*30)c. (40*70)/(20*60)d. (40/70)/(20/60)e. (40/60)/(30/70)18. A study is performed in which mothers of babies born with neural tube defects are questioned about theiracetaminophen consumption during the first trimester of pregnancy. At the same time, mothers of babies bornwithout neural tube defect are also questioned about their consumption of acetaminophen during the firsttrimester. Which of the following measures of association is most likely to be reported by investigators?a. Prevalenceb. Median survivalc. Relative riskd. Odds ratioe. Hazard ratio4

19. At a specific hospital, patients diagnosed with pancreatic carcinoma are asked about their current smokingstatus. At the same hospital, patients without pancreatic carcinoma are also asked about their current smokingstatus. The following table is constructed.SmokersNon-smokersTotalPancreatic Cancer504090No Pancreatic Cancer6080140Total110120230What is the odds ratio that a patient diagnosed with pancreatic cancer is a current smoker compared to apatient without pancreatic cancer?a. (50/90)/(60/140)b. (50/40)/(60/80)c. (50/110)/(40/120)d. (50/60)/(40/80)e. (90/230)/(140/230)20. The Third National Health and Nutrition Examination Survey was conducted in the United States in the 1990s toexamine the relationship between obesity and depression. The authors investigated the association betweenmajor depression and body mass index (BMI) for males and females (American Journal of Epidemiology.2003;158:1139-1147).BMI category, kg/m2Normal weight (BMI 18.5-24.9)Underweight (BMI 18.5)Overweight (BMI 25.0-29.9)Obese (BMI 30)Class 1 (BMI 30-34.9)Class 2 (BMI 35-39.9)Class 3 (BMI 40)Unadjusted Odds Ratio1.001.170.861.881.281.764.9895% Confidence Interval0.49 – 2.800.53 – 1.411.02 – 3.460.64 – 2.560.78 – 3.952.07 – 11.99From the table above, what is the correct interpretation of the overweight value of 0.86?a. Overweight individuals’ odds of having major depression are 14% lower than the odds of having majordepression for individuals with normal weight.b. Overweight individuals’ odds of having major depression are 14% higher than the odds of having majordepression for individuals with normal weight.c. An overweight individual has a 0.86 probability of having major depression.d. An overweight individual has a 0.86 odds of having major depression.5

21. As part of the Women’s Health Study, researchers investigated the role of systemic inflammation in predictingcardiovascular disease in women (N Engl J Med. 2002;347[20]:1557-1565). Researchers used a prospective studydesign with a large sample size. Blood levels of C-reactive protein (CRP) were measured at baseline and womenwere followed for an average of 8 years. The following table shows the relative risk estimates of cardiovascularevent (heart attack or stroke) within 5 years by quintile of CRP level for the 30,000 women. The first quintile isused as the reference category.10.49 mg/dLRelative RiskNumber ofwomen1.060002 0.49-1.08mg/dL1.86000Quintile of CRP Level3 1.08-2.09mg/dL2.360004 2.09-4.19mg/dL3.260005 4.19 mg/dL4.56000Based on the relative risk data above, one can conclude:a. There is no risk of heart attack/stroke for women with CRP levels in the first quintile.b. Decreasing CRP level appears to increase the risk of heart attack/stroke.c. Increasing CRP level appears to increase the risk of heart attack/stroke.d. There appears to be no association between CRP levels and heart attack/stroke.22. Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of anexposure’s effect on the risk of disease is called:a. Confoundingb. Biasc. Interactiond. Stratification23. The purpose of a double-blind or double-masked study is to:a. Achieve comparability of treated and untreated subjectsb. Reduce the effects of sampling variationc. Avoid observer and subject biasd. Avoid observer bias and sampling variation24. Randomization of study subjects in a clinical trial is most helpful for controlling for which of the following?a. Placebo effectb. Recall biasc. Non-complianced. Effect modification (interaction)e. Confounding25. A large-scale clinical trial is being planned to evaluate the effect of a non-selective beta-blocker on the clinicalcourse of portal hypertension. The primary outcomes of the study are all-cause mortality and majorgastrointestinal hemorrhage. The investigators are concerned about the possibility that episodes of majorgastrointestinal hemorrhage could be over-reported in the placebo group. Which of the following is the mostuseful technique to reduce this possibility?a. Randomizationb. Blindingc. Matchingd. Stratified analysis6

26. A case-control study is conducted to assess the association between alcohol consumption and lung cancer. 100patients with lung cancer and 100 controls are asked about their past alcohol consumption. According to thestudy results, alcohol consumption is strongly associated with lung cancer (OR 2.5). The researchers thendivide the study subjects into two groups: smokers and non-smokers. Subsequent statistical analysis does notreveal any association between alcohol consumption and lung cancer within either group. The scenariodescribed is an example of which of the following?a. Observer biasb. Confoundingc. Placebo effectd. Nonresponse biase. Recall bias27. A study is conducted to assess the relationship between race and end-stage renal disease. Two groups ofpathologists independently study specimens from 1,000 kidney biopsies. The first group of pathologists is awareof the race of the patient from whom the biopsy came, while the second group is blinded as to the patient’srace. The first group reports ‘hypertensive nephropathy’ much more frequently for black patients than thesecond group. Which of the following types of bias is most likely present in this study?a. Confoundingb. Nonresponse biasc. Recall biasd. Referral biase. Observer bias28. A study is conducted to assess the relationship between the use of an over-the-counter pain reliever duringpregnancy and the development of neural tube defects in offspring. Mothers whose children have neural tubedefects and age-matched controls with unaffected children are interviewed using a standard questionnaire. Thestudy shows that use of the pain reliever during pregnancy increases the risk of neural tube defects, even afteradjusting for race, other medications, family history of congenital abnormalities and serum folate level (OR 1.3, p 0.03). Which of the following biases is of major concern when interpreting the study results?a. Nonresponse biasb. Recall biasc. Observer biasd. Confoundinge. Selection bias7

Answers1a. A1b. B1c. D1d.