It's a biostatistics lecture. MCQ are made according to BCPS guideline part 1 for all specialty

1. Exercise on Study Design
Prof Md Anisur Rahman (Anjum)
Prof & Head of the department
Ophthalmology. Dhaka Medical College.
Dhaka
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2. Exercise: 1
 A researcher with a medium-sized grant wants to study the
relationship between exposure to in-home treated drinking
water (such as Brita filters) and diarrhea among children in
three neighboring towns, in comparison to tap water. All three
towns use the same water source and treatment facility.
 Which study design should the researcher choose and how
might she study this relationship?
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3. Answer of Exercise: 1.
Cohort study. The researcher may randomly select 250
households with children to study and then determine
exposure status (whether the family uses regular tap water or
an in-home treatment). The researcher would analyze daily
logs of each household to gather data on cases of the
outcome (diarrhea) among the children and then compare the
number and frequency of diarrhea cases in the exposure
(home-treated water) and the control (tap water) groups.
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4. Exercise: 2.
 A researcher wants to survey the prevalence of STIs among
female college students at four universities. Two of these
universities have large educational and outreach campaigns
for sexual protection and testing, while the other two do not.
The researcher has very limited time and funds.
 Which study design should the researcher choose and how
might she study this relationship?
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5. Answer of Exercise: 2.
 Cross-sectional . For the cross-sectional study, researchers can
survey all or a sample of female students about their STI
status; for the ecological study, campus health records over
the last year can provide data on female students diagnosed
with STIs.
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6. Exercise: 3
 A researcher wants to study whether women who breastfeed
have lower rates of breast cancer in later life. Funders would
like an analysis within one to two years.
 Which study design should the researcher choose and how
might she study this relationship?
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7. Answer of Exercise: 3.
• Case-control study. The researcher would enroll women with
the outcome (women with breast cancer who have had
children) to be cases and then match four times as many
women as controls (women without breast cancer who have
had children and are similar in age, SES, and health care
access as the cases).
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8. Answer of Exercise: 3
• They would then interview all the women about their nursing
histories and record data on whether and how long the
women breastfed. The researchers can also collect data on
other factors that may affect the outcome. From this data,
they can examine whether women with breast cancer had
significantly less utilization of (in other words, exposure to)
breastfeeding than similar women who did not develop breast
cancer.
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9. Exercise: 4
 A 39-year old woman presents with a mild sore throat, fever,
malaise and headache and is treated with penicillin, for
presumed streptococcal infection. She returns in a week with
hypertension, fever, rash and abdominal pain. She responds
favorably to chloramphenicol, after a diagnosis of Rocky
Mountain spotted fever is made.
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10. Answer of Exercise: 4
 This is a case report. It is not usually regarded as an
"epidemiologic" study, since there is neither "population" nor
comparison group. Presentation of an interesting case can
serve to alert other health care professionals of the possibility
of misdiagnosing a potentially fatal disease.
• http://www.epidemiolog.net/epid168/labs/AnalyticStudExerI
nstGuid2000.pdf
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11. Exercise: 5
• Cryptosporidiosis is an enteric illness that is frequently
waterborne. Khalakdina and colleagues (2003) could find no
published study of the risk factors for cryptosporidiosis in
immunocompetent adults. Patients with cryptosporidiosis
were recruited from a surveillance system, and age-matched
controls were recruited by random-digit dialing. Subjects in
both groups were interviewed by telephone to obtain
information about previous disease.
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12. Answer of Exercise: 5
 At first glance this study might appear to be cross-sectional
because a telephone interview was used. However, the data
collected pertained to disease that occurred after exposure of
the cryptosporodiasis (for the case). Therefore, this study is
best described as case-control.
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13. Exercise: 6
Brown and coworkers (2003) designed a study to determine the
efficacy of immunotherapy with ant venom for treating ant
stings. The study involved a group of adults who were allergic
to ant stings; each subject was randomly assigned to receive
either venom immunotherapy or a placebo. After a sting
challenge in which any reactions were recorded, the group
originally on the placebo was given the venom
immunotherapy, and after a sufficient time, they too were
given a sting challenge.3/18/2017 13

14. Answer of Exercise: 6
• This is not a classic crossover clinical trial because patients
who received the therapy were not subsequently given a
placebo. Why would a modified crossover study be necessary
in this study?
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15. The study design is interesting, and some might be tempted to
call it case-control. The purpose was to compare self-reported
therapy with actual therapy. Both of these measures (self-
reported and actual) occurred at the same time, so the study
also has some characteristics of a cross-sectional study. Our
opinion is that the study is case-control, but it illustrates the
difficulty in classifying studies cleanly into any scheme.
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Answer of Exercise: 6

16. 1) Following are the characteristic of case control study:
a) Case-control study is usually retrospective.
b) Useful for hypothesis generation
c) Can only look at one outcome
d) Bias is a major problem
e) We measure relative risk in case control study
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17. a b c d e
T T T T F
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18. 2) Following are the characteristic of Cohort studies
a) Cohort studies describe incidence or natural history.
b) Retrospective cohorts where available are cheaper and
quicker.
c) Confounding variables are the major problem in analysing
cohort studies.
d) Subject selection and loss to follow is more in case control
study than cohort study
e) Cohorts are heterogeneous people
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19. a b c d e
T T T F F
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20. 3) ________Is the classical form of research
a) Case control study
b) Cohort study
c) Experimental study
d) Cross-sectional study
e) Longitudinal study
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21. a b c d e
F F T F F
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22. 4) Which of the following is/are advantage of Case Control
Studies?
a) They can simultaneously look at multiple risk factors
b) They are useful to initially establish an association between a
risk factor and a disease or outcome
c) They take less time to complete because the condition or
disease has already occurred
d) Unable to estimate incidence rates of disease
e) a, b, and c
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23. a b c d e
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24. 6) In a case-control study to investigate oral contraception and
breast cancer:
a) Cases would be women with breast cancer.
b) Controls would be given oral contraception.
c) Cases would be given oral contraception.
d) Women with breast cancer would be randomly allocated to be
cases or controls.
e) Controls would be observed for several years to see how
many developed breast cancer.
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25. a b c d e
T F F F F
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26. 7) In a case-control study, patients with lung cancer had a highly
significantly lower cholesterol level than did controls. This
provides strong evidence that:
a) Low cholesterol causes lung cancer.
b) Here is evidence for a relationship between low cholesterol
and lung cancer in the sampled population.
c) Low cholesterol is not related to lung cancer.
d) Low cholesterol and lung cancer always go together.
e) Low cholesterol is a risk factor for the development of lung
cancer.
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27. a b c d e
F T F F F
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28. 8) In a well designed clinical trial of treatment of ovarian cancer,
remission rate at one year is similar for a new drug and usual
care, The P-value is 0.4. This means that
a) Both treatments are effective
b) Neither treatment is effective
c) The statistical power of this study is 60%
d) The best estimate of treatment effect is 0,4
e) It is not possible to decide on whether one treatment is better
than the other using this information alone
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29. a b c d E
F F F F T
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30. 9) Which of the following would occur in a longitudinal study?
a) Measures are taken from different participants over an
extended period of time.
b) Participation is expected to last for a minimum of 24 hours.
c) Measures are taken from the same participants on different
occasions usually over extended periods of time.
d) Measures are taken from participants in at least six different
countries.
e) Measures more than twice
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31. a b c d e
F F T F T
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32. 10) The hallmark feature of an analytic epidemiologic study is:
(Choose one best answer)
a) Use of an appropriate comparison group
b) Laboratory confirmation of the diagnosis
c) Publication in a peer-reviewed journal
d) Statistical analysis using logistic regression
e) Sample will be non randomly allocated
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33. a b c d e
T F F F F
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