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Sample exam questions for Introduction to Epidemiology and Public Health
Note: Questions can be multiple choice (indicate the one correct answer) or multiple response
(squares

indicate all answers that are correct).
1.
To be causally associated with
disease, the etiological factor should fulfill the following criteria:
Indicate all that apply.

The factor is present in all subjects with the disease.

Elimination of the factor reduces risk of the disease.

The exposure to this factor should p
recede the development of the disease.

The factor is more prevalent among those with the disease than among those without the
disease.
2.
At the start of a cohort study the exposure is determined with the help of a questionnaire. During
the study the
re is no "loss to follow
up". At the end of the follow
up time the number of cases is
known and is divided into exposed and unexposed. The odds ratio (OR) is used as the
association measure. Which comment is the most appropriate here?
a.
Researchers should ha
ve better calculated the risk ratio (=incidence proportion ratio).
b.
The OR has no useful interpretation.
c.
Researchers should have better calculated the incidence rate ratio.
d.
The OR approaches the incidence rate ratio.
3.
During a study of 20 years five people
are followed to measure the occurrence of upper
respiratory tract infection. As this infection can occur more than once, all disease events are
included in this study.

1 person is lost to follow
up after 1.5 years.

2 persons died respectively after 10 and
15 years from a different cause.

1 person got the first respiratory tract infection after seven years and the second infection
after 12 years of follow
up. Both infections take half a year of recovery. This person is
followed
up until the end of the
study.

One person is followed
up the whole period without occurrence of disease.
What is de incidence rate in this study ?
a.
0.06 per person
year
b.
0.03 per person
year
c.
0.15 per person
year
d.
0.08 per person
year
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4.
What is the fraction of cases with the disease
among the exposed that is attributable to the
exposure?
Unexposed
Exposed
Disease
9
17
No disease
7
5
a.
0.27
b.
0.60
c.
0.30
d.
0.77
5.
The incidence rate (IR) differs from the incidence proportion (IP) because...
e.
IP can be assessed in a closed population, IR
not.
f.
IR can be assessed in an open population, IP not.
g.
IP takes competing mortality into account; IR does not.
h.
IR can be assessed more precisely than IP
6.
If you want to know the proportion of the disease that could be prevented by eliminating the
exposur
e in the entire study population, you should calculate the
a.
attributable fraction
b.
attributable risk
c.
population attributable risk percentage
d.
negative predictive value
7.
Precise measurement of exposure is important in epidemiologic research. Namely, when the
exposure is
not
precisely measured the association between exposure and effect is likely to be...
a.
overestimated
b.
confounded
c.
underestimated
d.
random
8.
Which of the following designs is/are suitable for studying a genetic polymorphism in relation to
risk of diabetes mellitus?
Indicate all that apply.

Case
control study

Cross
sectional study

Cohort study

Randomized, controlled trial
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9.
The
Cancer and Steroid Hormone (CASH) study, in which women with breast cancer and a
comparable group of women without breast cancer were asked about their prior use of oral
contraceptives is an example of which type(s) of study?
Indicate all that apply.

clinical trial

cohort study

cross sectional survey

case
control study

observational study

experimental study
10.
The precision of an estimate of a relative risk depends on the ...
a.
generalisability
b.
size of the stud
y
c.
validity of the s
tud
y
d.
presence of bias
11.
In a cohort study the relative risk for COPD for moderate smokers versus non
smokers was 4.
For heavy smokers compared to non
smokers the relative risk was 10.
What would have been the relative risk for COPD in this study if the hea
vy smokers were used
as the reference category?
a.
for non
smoking 0.1 and for moderate smoking 0.4
b.
for non
smoking 0.2 and for moderate smoking 0.6
c.
for non
smoking 4 and for heavy smoking 10
d.
this cannot be calculated with the available data
12.
An epidemiologi
st in Tanzania wants to study the efficacy of iron supplementation for the
prevention of HIV infection. He wants to make sure that only subjects who are (still) free of HIV
infection are enrolled in his trial. Therefore, he screens a large group of people
using a
diagnostic test. Based on the outcome of the test, he decides who could participate in his iron
supplementation trial.
For this purpose, it is very important that the diagnostic test has a high...
a.
sensitivity
b.
positive predictive value
c.
specificity
d.
negative predictive value
13.
A diabetes test is being applied in a population of 5000 men. Previous evaluation of the diabetes
test in a different population showed a sensitivity of 70% and an specificity of 80%. The
prevalence of diabetes is 0.5%.
What is
the diagnostic value of a
positive
test in this situation?
a.
2%
b.
47 %
c.
4%
d.
7
0%
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14.
Information bias in a cohort study can be avoided by ensuring that...
Indicate all that apply.

no competing diseases do occur.

follow
up is complete.

the persons
who assess the disease are not aware of the exposure of the participant.

disease assessment is highly standardized.

the persons who collect the data are not aware of the study hypothesis.
15.
A cohort study shows a RR of 1.8 (95% CI 1.4
2.2) for alco
hol consumption and breast cancer.
Another cohort study shows a RR of 1.8 (95% CI 0.6
3.5) for smoking and breast cancer.
What can be concluded from the results of this study?
Indicate all that apply.

Both
associations are likely to be due to chance.

Both
associations are biased.

The study on smoking is probably smaller than the study on alcohol.

Alcohol and smoking both cause breast cancer.
16.
When studying diet and risk of chronic diseases, a cohort study generally has the following
advan
tage compared to a case
control study:
a.
Potential confounders can be taken into account
b.
Selection bias does not occur
c.
Various dietary exposures can be studied at the same time
d.
It has higher internal validity
17.
What is a disadvantage of a cohort study
compared to a clinical trial?
a.
The external validity is lower
b.
It is more prone to confounding
c.
It is less suitable for studying clinical outcomes
d.
Participants can drop out during follow
up
18.
The Framingham Study, in which a group of residents have been follo
wed since the 1950s to
identify occurrence and risk factors for heart disease, is an example of which type(s) of study?

cohort

case
control

experimental

observational

clinical trial

cross
sectional
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19.
Researchers prospectively
follow a group of 100 vegetarians and 200 non
vegetarians.
After 30 years of follow
up, 8 of the vegetarians and 20 of the non
vegetarians develop heart
disease. The 95% confidence interval on the relative risk of 0.8 ranges from 0.6 to 0.9.
Select the be
st statement.
a.
Vegetarians were 80% less likely to develop heart disease during 30 years of follow
up
compared with
non
vegetarians.
b.
The researchers should have calculated an odds ratio rather than a relative risk.
c.
The relative risk of 0.8 is not statisti
cally significant as the 95% confidence interval contains
the value 0.8.
d.
Vegetarians were 20% less likely to develop heart disease during 30 years of follow
up
compared with
non
vegetarians.
20.
In the Netherlands there is an increase in the prevalence of
cardiovascular diseases.
This is a consequence of
a.
deterioration of the food pattern
b.
increase in hypertension
c.
improved treatment
d.
increase in obesity
21.
General practitioners decide to intensify pharmacological treatment of patients when their
absolute
10
year risk of cardiovascular mortality exceeds 20%. Which risk factors form the basis
for calculating this absolute risk?
a.
Age, gender, smoking,
isolated systolic hypertension
an
d
serum
triglyceride levels
b.
Age, gender, smoking, blood
pressure an
d
presence
of diabetes mellitus
c.
Age, gender, smoking, systolic blood
pressure an
d
serum total cholesterol
d.
Age, gender, smoking,
body mass index and family history
22.
In a hospital
based study of the association between coffee consumption and the occurrence of
stroke,
a group of patients hospitalized after suffering a stroke was compared to a control
population hospitalized for other reasons. The patients hospitalized for stroke were found to
consume significantly more coffee than the controls.
All of the following sta
tements represent possible explanations for the observed positive
association between coffee consumption and stroke,
EXCEPT
:
a.
Heavy coffee consumers may also be heavy smokers, so smoking rather than coffee drinking
is the relevant causal factor
b.
The patien
ts restricted their coffee intake after suffering a stroke.
c.
The hospitalized controls consume less coffee, on the average, than individuals in the general
population, resulting in a spurious association between coffee consumption and stroke.
d.
Excessive co
ffee consumption can cause a stroke.
23.
Select the correct statement concerning the selection of controls in a case
control study:
a.
Randomization can help assure comparability of cases and controls.
b.
Matching can be used to reduce confounding bias.
c.
It is best to identify controls with conditions that are related to the outcome in the case
control
study.
d.
It is less important to assure comparability of cases and controls in a case control study than
comparability of study arms in a randomized controll
ed trial.
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24.
In a case
control study the association was examined between smoking and risk of Parkinson's
disease. The table below provides the results.
Which of the following odds ratios is correct?
Controls
Cases
Smokers
55
30
Non smokers
45
70
a.
0.35
b.
2.85
c.
1.83
d.
0.55
25.
Indicate
three
types of cancers that are most frequently occurring in Westernized countries.

lymphoma

bladder cancer

cervical cancer

colon cancer

prostate cancer

breast cancer
26.
An epidemiologist performed
a double
blind, randomized, placebo
controlled trial to examine the
effect of fish oil supplementation on memory complaints. In the group that received fish oil, 19%
of the participants forgot to take their daily supplements during the study whereas this
was only
3% in the placebo group. Is this a problem?
a.
Yes, because
this affects the external validity of the study.
b.
Yes, because
the study outcome can be biased.
c.
No, because participants and investigators were blinded towards the type of treatment in both
g
roups
d.
No, because all confounders were equally distributed over both groups due to randomization
27.
An epidemiologist wants to assess the effect of tea drinking on blood pressure. He decides to do
an intervention study.
Which of the following measures does
not
increase the internal validity of the study?
a.
Careful monitoring of blood pressure during the study
b.
Inclusion of a control group
c.
Randomization
d.
Random selection of participants from the general population
28.
The main advantage of a randomized controlled
trial (RTC) compared to all other epidemiology
study designs is that the RCT:
a.
equally distributes characteristics that may be independent risk factors for the outcome of
interest over the study arms.
b.
is prospective thereby eliminating the need for histor
ical data.
c.
is less expensive.
d.
guarantees that confounding bias will not occur.
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29.
A pharmaceutical company showed the following in an article: "1500 subjects with a cold were
treated with our new medicine. Within three days, 95% were asymptomatic and
this result was
statistically significant." The company claims the new medicine was effective.
Is this conclusion justified?
a.
Yes, because the effect was very large (95% of the subjects benefitted from treatment).
b.
No, because statistical significance indic
ates that the null hypothesis ("no effect") was correct.
c.
No, because no control group was involved in the study.
d.
Yes, because the effect of treatment could not be explained by chance.
30.
Public health surveillance includes various activities.
Which one
is not part of public health surveillance?
a.
Data collection
b.
Data dissemination
c.
Disease control
d.
Data analysis
31.
The problem of confounding can be solved by...
a.
ch
o
osing a prospective design.
b.
increasing the precision of the measurements.
c.
stratification during
data analysis.
d.
this cannot be solved.
32.
The number of DALYs (Disability Adjusted Life Years) lost in each person's life history can be
calculated. By combining all life histories in this population of three persons, the population
health in terms of
DALYs can be described for this population.
Which of the following combinations is correct?
a.
In the life history of person A 35 DALYs are lost and the total loss of DALYs for the population
of three is 70
b.
In the life history of person A 15 DALYs are lost a
nd the total loss of DALYs for the population
of three is 55.5
c.
In the life history of person B 5 DALYs are lost and the total loss of DALYs for the population
of three is 9.5
d.
In the life history of person C 19.5 DALYs are lost and the total loss of DALYs f
or the
population of three is 79.5
33.
In a study on the prevalence of disease X in nursing homes A and B you get the following data.
Nursing home A = index 1
Age
Persons
Number of cases
with disease X
Prevalence rate
(per 100)
Young
200
4
2.0
Old
400
24
6.0
Total
600
28
4.7
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Nursing home B = index 2
Age
Persons
Number of cases
with disease X
Prevalence rate
(per 100)
Young
800
24
3.0
Old
100
8
8.0
Total
900
32
3.6
Nursing home A + B = standard
Age
Persons
Number of cases
with disease X
Prevalence rate
(per 100)
Young
Old
Total
One can calculate the standardi
z
ed prevalence rate and comparative mortality figure (CMF) by
means of direct standardization, using the joint population of nursing home A and B as the
standard.
Which calculation is correct?
a.
The standardized rate of nursing home A is 3.3/100
b.
The CMF of nursing home A is 0.97
c.
The standardized rate of nursing home A is 2.4/100
d.
The standardized rate of nursing home B is 6.3/10