Download CDM USMLE Type Questions with answers

CDM USMLE Type Questions
12/8
EBM
1. An epidemiology wants to use Kaplan-Meier method to construct a life table for workers with
lead exposure. Which of the following data is necessary for this endeavor?
a. Number of workers lost to follow up
b. Causes of death of workers during study period
c. Exposures of the workers at beginning of the study period
d. Specific diseases contracted by workers during the study period
e. Health statuses of the workers at the beginning of the study period
2. As a physician you are asked to assist in recruitment of some of your cancer patients for a study
trying to establish a link between prior pesticide exposure and cancer. What study design best
describes this research?
a. Cohort
b. Randomized trial
c. Cross-sectional
d. Case-control
e. Ecological
3. A new screening test has been recommended for a disease. A small study of 5000 patients is
used to determine its sensitivity. What is the sensitivity of the test?
a. .32
b. .68
c. .80
d. .25
e. .77
4. A new screening test for colorectal cancer has been developed. An oncologist would like to see
suspected cases screened with this test. Which test parameter best describes the ability of the
test to correctly identify a cancer free patient?
a. Sensitivity
b. Pos predictive value
c. Specificity
d. Neg predictive value (prob of cancer-free pt given that they have a negative test – as
opposed to this one where we already know the pt is disease-free)
e. Positive likelihood
5. What type of study would be best to evaluate a new drug proposed to lower cholesterol versus
a standard drug, Lipitor?
a. Cohort study
b. Randomized trial
c. Case-control study
d. Cross-sectional study
e. Ecological study
6. A study was conducted to look at the cases of hypertension in relation to their fiber
intake. What is the odd ratio (OR) for hypertension in this case-control study, comparing high
fiber consumers to low fiber consumers?
a. 1.38
b. 0.4
c. 0.55
d. 0.73
e. 1.22
7. Z-scores (values) are used incomputing confidence limits. They correspond to the standard
normal distribution expressed in standard deviations. Which z-score is used for computing 95%
confidence intervals?
a. 1.64
b. 1.96
c. 2.58
d. 2.76 (99% CI)
e. 3.00
8. In a case control study of alcohol consumption and liver cancer, cases over-report alcohol
consumption, attributing this to their cancer. What type of bias is this?
a. Selection bias
b. Confounding (would require third variable that would alter relationship between alcohol
and cancer)
c. Random bias
d. Recall bias (does not involve forgetting info)
e. Lead-time bias
9. In a cohort study of obesity and risk of type 2 diabetes, the loss to follow-up is 30% among the
obese subjects and 10% among the non-obese subjects. What effect will this most likely have
on the calculated relative risk (RR)?
a. Overestimation
b. Underestimation
c. No change
d. Cannot determine
10. The incidence rate of myocardial infarction over the observation period was:
a. 3/6 = 0.5 cases/person year
b. 3/10
c. 2/15
d. 3/15
e. 3/5
11. The statistical method most appropriate to analyze the means of the four groups is
a. T-test (2 groups)
b. ANOVA (used for more than two groups)
c. Linear regression
d. Correlation
e. Logistic regression
12. A cohort study is performed to evaluate the relationship between inflammation as measured by
a high C-reactive protein and the occurrence of myocardial infarction among women. In the
study, 500 subjects with High CRP and 500 with normal CRP are studied over 20 year
period. During study, 50 of the women with high CRP and 15 with normal develop a newly
diagnosed myocardial infarction.Incidence rate (per 10000 erson years) for a myocardial
infarction for a persion with normal CRP is
a. 15 .
13. A study was undertaken to evaluate the use of computed tomography in the diagnosis of lumbar
disk herniation. 80 pts with lumbar disk herniation confirmed by surgery were evaluated, as
were 50 without. CT results positive in 56 of pts with herniation and 10 without. Sensitivity =
a. 56/80
14. MESSED UP QUESTION If the relationship between two measures is linear and the coefficient of
determination has a value near 1, a scatterplot of the observations
a. Is horizontal straight line
b. Is vertical straight line
c. Has positive slope
d. Has negative slope
e. Is a straight line that is neither horizontal nor vertical
15. In a placebo-controlled trial of the use of oral aspirin-dipyridamole to prevent arterial restenosis
after coronary angioplasty, 45% of pts receiving the drug has restenosis, 46% receiving placebo
had restenosis. In reporting this finding, the authors stated p > 0.05 which means
a. Probability is greater than 1 in 20 that a difference this large could occur by chance
alone
16. A study was undertaken to evaluate any increased risk of breast cancer among women who use
birth control pills. The RR was calculated. A type I error in this study consists of concluding
a. A significant increase in RR when RR is actually > 1
b. Significant increase in RR when RR is actually < 1
c. Significant increase in RR when RR is actually 1
d. No significant increase in RR when RR is actually 1
e. No significant increase in RR when the RR is actually > 1
17. Supposed the confidence limits for the mean of a variable are 8.55 and 8.65. These limits are
a. Less precise but have a higher confidence than 8.1 and 9.5
b. More precise but have a higher confidence than 8.1 and 9.5
c. More precise but have a lower confidence than 8.1 and 9.5
d. Less precise but have a lower confidence than 8.1 and 9.5
e. Cannot be determined
18. A study was undertaken to compare treatment options in black and white patients who are
diagnosed as having breast cancer. The 95% CI for the odds ratio for blacks being more likely to
be untreated than whites was 1.4 to 3. The statement that most accurately describes the
meaning of these limits is that
a. 95% of the odds radios fall within these limits
b. 95% of the time blacks are more likely than whites to be untreated
c. No difference exists in the treatment of black and white women
d. Black women are up to 3 times more likely than whites to be untreated
e. White women are up to 3 times more likely than black to be untreated
19. The ability to assign by chance the type of antihypertensive agent used reduces the likelihood of
confounding of diet and physical activity in a study of treatment of BP elevation. What is the
most appropriate study design for this research?
a. Case control
b. Cohort
c. Ecological
d. Cross-sectional
e. Randomized clinical
20. An eval of an antibiotic in the tx of possible occult baacteremia was undertaken. 500 children
with fever but no focal infection were randomly assigned to the abx or to a placebo. A blood
sample for culture was obtained prior to beginning therapy and all pateitns were reevaluated
after 48 hours. The authors reported the proportion of children with major infectious morbidity
among those with bacteremia was 13% in the placebo group and 10% in the antibiotic
group. The 95% CI for the difference was proportions was -2/6% to +8.6%. Thus, the most
important conclusion is that
a. The diff in major infectious morbidity between plcebo and antibiotic is statistically
significant
b. The proportion of children with major infectious morbidity is the same with placebo and
antibiotic
c. No statistically significant difference exists in the proportions that received placebo and
antibiotic
d. The study has low power to detect a difference owing to the small sample sze and no
conclusions should be drawn until a larger study is done
e. Using a chi-square test to determine significance is preferable to determining a CI for
the difference
21. In a sample of 49 people, the mean total leukocute count id found to be 7600 cells/mm3, with
SD of 1400. Assuming a normal distribution of counts, a randomly selected individual has a total
leukocyte count lower than 4800
a. 1% of the time
b. 2.5 % of the time (2 SD = 95%, divide by 2 for just those on the L side of the curve)
c. 5% of the time
d. 10% of the time
e. 15% of the time
22. In an epidemiologic study of carbon-black workers, 500 workers with respiratory disease and
200 without were selected for study. The investigators obtained a history of exposure to carbonblack dust in both groups. Among workers with disease, 250 had history of exposure, 50 of
those without had a history. What type of study?
a. Cohort (classify based on exposure status, then follow forward to find those that
develop the outcome)
b. Case-control (identify people with a disease and without, then ask about prior exposure
that may have precipitated)
c. Cross-sectional
d. Randomized clinical
e. Ecological
23. A study undertaken to evaluate the use of CT in the diagnosis of lumbar disk herniation. 80 with
lumbar disk herniation confirmed by surgery were evaluated with Ct, as were 50 pts without
herniation. The CT results were positive in 56 of the pts with herniation and in 10 of the pts
without. What is the false-positie rate?
a. 10/50 = 20%
b. 25/80 = 30%
c. 56/80
d. 40/50
e. 56/66
24. Scale used in measuring cholesterol is
a. Ordinal (ranked values – like strongly agree, agree, neutral, disagree, etc.)
b. Discrete (rather continuous range of values)
c. Nominal
d. Qualitative
e. Interval
25. Which of the following sources is most likely to provide an accurate estimate of prevalence of
MS in a community?
a. Survey of practicing physicians to ask how many MS patients they are currently treating
b. Info from hospital discharge summaries
c. Data from autopsy reports
d. Telephone survey of a sample of randomly selected homes asking how many people in
home have disease
e. Examination of medical records of a representative sample of people living in the
community
26. A significant positive correlation has been observed between alcohol consumption and the level
of systolic BP in men. From this correlation, we may conclude that:
a. No association exists between alcohol and systolic pressure
b. Men who consume less alcohol are at lower risk for increased systolic
c. Men who consume less are at higher risk for increased systolic
d. High alcohol can cause increased systolic pressure (correlation, not causation)
e. Low alcohol can cause increased systolic pressure
27. A population distribution plot of cholesterol levels among healthy and diseased individuals is
shown. In defining a cut-off value for disease screening, which of the following characteristics
best describes line 2?
a. High Se, high PPV
b. High Se, low PPV
c. High Se, high NPV
d. High Se, high PPV
e. High accuracy
28. A researcher develops a new test to detect lung cancer at an earlier stage. The test picks up the
lung cancer in 85% of pts with lung cancer diagnosed by the gold standard and is negative in
90% of pts without lung cancer. The prevalence of lung cancer in pop is 3%. What is the
sensitivity
a. 15%
b. 60%
c. 85%
d. 87.5%
e. 90%
29. An investigator wnts to study the effects of smoking on subsequent development of lung
cancer. She gathers a group of 100 smokers and 100 non-smokers and foloows them for 20
years to compare rates of development of lung cancer. What type of study?
a. Cohort study
30. The ELISA for HIV virus has a sensitivity and specificity of 99.9%. Therefore, in a pop of 100,000
people where the prevalence is 1%, there will be 1 false negatives and 99 false
positives. Likewise, there will be 999 true positives and 98,901 true negatives.
a. 1000 HIV+: 999 true +, 1 true –
b. 99000 HIV-: 98901 true+, 99 true –
c. If an analysis was made of a blood donor pool in which blood had already been screened
for HIV and now the prevalence of HIV was 0.1%, how would the sensitivity, specificity,
PPV and NPV change?
d. Decreased Se and Sp, same PPV and NPV
e. Decreased Se, Sp, PPV, NPV
f. Same Se, Sp, PPV, and NPV
g. Same Se and Sp, decreased PPV and NPV
h. Same Se and Sp, decreased PPV, increased NPV (fewer positive cases, so less likely you’ll
have positive test; more negative cases, so more likely you’ll get a negative test –
prevalence only chances predictive vlues)
31. Chicken pox is slowly taking over the entire med student community (3000 students). In 2008,
the prevalence of this disease within this community was 10%. In 2009, 270 new cases were
reported. What is the incidence of this chicken pox within this student population in 2009?
a. 5%
b. 9%
c. 10% (at risk population is 3000-300 for those that already got it last year)
d. 15%
e. 19%
32. At UT, a study of pulse rates was conducted on 1000 students. The mean pulse rate was 75 and
the standard deviation was 10. Which is true?
a. Approx 99.7% had pulse between 75 and 85
b. Approx 95% had pulse rate between 65 and 85 (95% = 2 SD above and below)
c. Approx 68% between 65 and 85
d. Approx 95% between 65 and 75
e. Approx 99.7% between 65 and 85
33. A researcher is using the 15-point Borg Scale of Pereived Exertion in an exervise study. The
minimum score of 6 indicates 20% effort and the maximum score of 20 indicates
exhaustion. What type of variable?
a. Nominal
b. Interval
c. Discrete
d. Ratio
e. Ordinal (ranked scale ranking how tired you are)
34. A one year study was conducted to look at risk of developing CHD in relation to their BP
status. What is the RR for CHD inthis cohort study, comparing hypertensives to normotensives?
a. 9.33
b. 0.11
c. 2.33
d. 0.29
e. 3.50
35. A researcher develops a new test to detect lung cancer at an earlier stage. The test picks up the
lung cancer in 80% with lung cancer, and is negative in 90% of those without. What is
sensitivity?
a. 5%
b. 10%
c. 80%
d. 85%
e. 90%
Answers:
1. A
2. D
3. E
4. C
5. B
6. C
7. B
8. D
9. B
10. D
11. B
12. A
13. A
14. C, E
15. A
16. C
17. C
18. D
19. E
20. C
21. B
22. B
23. A
24. B
25. E
26. B
27. B, C
28. C
29. A
30. H
31. C
32. C
33. E
34. E
35. C