SECTION B (42 mks)

Instructions: Each question below contains suggested responses. Select the one (unless stated otherwise) best response to each question. Two marks per question. Answer all questions.

1.One of the fundamental premises underlying the study of epidemiology is...

A.Disease, illness and ill health are randomly distributed in a population.

B.Disease, illness and ill health are not randomly distributed in a population.

C.Disease, illness and ill health are only randomly distributed in large populations.

D.Disease, illness and ill health are very rarely distributed in large populations.

E.None of the above.

2.Which of the following best describes the retrospective design where subjects are sampled by disease status and is often used when the investigator is interested in rare diseases.

A.Intervention trial

B.Case control study

C.Retrospective cohort

D.Ecologic study

E.None of the above

3.Which of the following best describes the study design that is often used when the investigators are interested in rare exposures.

A.Intervention trials

B.Cohort studies

C.Prevalence studies

D.Case control study

E.None of the above

4.A cohort study differs from a case-control study in that:

A.Subjects are enrolled or categorized on the basis of their exposure status in a cohort study but not in a case-control study

B.Subjects are asked about their exposure status in a cohort study but not in a case-control study

C.Cohort studies require many years to conduct, but case-control studies do not

D.Cohort studies are conducted to investigate chronic diseases, case-control studies are used for infectious diseases

5.Given the area under a normal curve, which two of the following ranges are the same? (Circle the TWO that are the same.) [4 Marks]

A. From the 2.5th percentile to the 97.5th percentile

B. From the 5th percentile to the 95th percentile

C. From the 25th percentile to the 75th percentile

D. From 1 standard deviation below the mean to 1 standard deviation above the mean

E. From 1.96 standard deviations below the mean to 1.96 standard deviations above the mean

6.The primary use of the standard error of the mean is in calculating the:

A. Confidence interval

B. Error rate

C. Standard deviation

D. Variance

7.Which of the following best describes the study design that can be either retrospective or prospective and is often used when the investigators are interested in rare exposures.

1. Intervention trials
2. Cohort studies
3. Prevalence studies
4. Case control study
5. None of the above

8.The strength of an association is one of the criteria for evaluating the cause and effect relationship between an exposure and outcome. Which of the following is a measure of the strength of association?

1. Incidence rate among the exposed
2. Cumulative incidence among the exposed
3. The ratio of odds of exposure among cases to the odds of exposure among the non-cases
4. Odds of disease among exposed relative to the prevalence of exposure in the source population
5. None of the above

9.Indicate if the following statement is true or false

A risk ratio measure and a correlation coefficient are both measures of association.

A.TRUE

B.FALSE

10. Indicate if the following statement is true or false

A population attributable risk proportion depends on the prevalence of exposure and is not directly related to the strength of an association.

A.TRUE

B.FALSE

11. Indicate if the following statement is true or false

The study base for a case-control study consists of those people who if they developed the disease could have been counted as cases.

A.TRUE

B.FALSE

12. Which of the following measures is used frequently as a denominator to calculate the incidence rate of a disease?

A.Number of cases observed

B.Number of new cases observed

C.Number of symptomatic cases

D.Person-years of observation

E.Persons lost to follow-up

13. In a case-control study the association between smoking and risk of pulmonary disease was examined. Results are presented in the table below. 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

14. Which of the following results give the reader the most information concerning statistical significance, sample size and strength of association?

A.A relative risk of 2.5 with a 95% CI of 2.0 to 3.1

B.A p-value of 0.0004 with an alpha = 0.05

C.A p-value of <0.05 and a relative risk of 2.5

D.A relative risk of 5.0 and a statistical power of 0.70

E.None of the above

15. A study was conducted to evaluate the association between benzene exposure and leukemia. Employment records identified 10,000 workers who were occupationally exposed to benzene in the 1980s and 14,000 workers who were not occupationally exposed to benzene. These records were subsequently linked with cancer registries to identify cases of leukemia from 1990 to 2000. During this time there were 250 cases of leukemia among the benzene-exposed workers and 120 cases among the unexposed workers.

What is the risk of leukemia among workers who were exposed to benzene?

A.0.25 within 10 years

B.0.025 within 10 years

C.250 per 1000 person years within 10 years

D.25 per 10 000 within 10 years

In nine families surveyed, the numbers of children per family were 4, 6, 2, 2, 4, 3, 2, 1 and 7. Answer the next few questions based on these data.

16. The mean, median, and mode numbers of children per family respectively are:

A.3.4, 2, 3

B.3, 3.4, 2

C.3, 3, 2

D.2, 3.5, 3

E.None of the above

17. The range of number of children per family is

A.1

B.2

C.3

D.4

E.6

18. Which of the following is true about the distribution of the number of children per family

A.The distribution has zero skewness

B.The distribution is positively skewed

C.The distribution is negatively skewed

D.It is a symmetrical distribution

E.None of the above

19. All the following statements are true of a normal distribution EXCEPT

A.the mean=median=mode

B.about 95 percent of observations fall within 2 standard deviations of the mean

C.approximately 68 percent of observations fall within 1 standard deviation of the mean

D.the number of observations between 0 and 1 standard deviation from the mean is the same as the number between 1 and 2 standard deviations from the mean

E.the shape of the curve does not depend on the value of the mean

20. In a large well designed randomized controlled trial of treatment of cervical cancer, remission rate at 3 years is similar for the new drug and the standard of care. The p-value is 0.4; what does this value mean?

A.The statistical power of the study is 60%

B.The best estimate of treatment effect is 0.4

C.It is not possible to decide whether one treatment is better than the other with this information alone

D.Neither treatment is effective

E.Both treatments are effective