1.Select the best answer

A.Randomized controlled trials are considered the "gold standard" of epidemiology study designs because randomization guarantees comparability of study arms.

B.A weakness of randomized controlled trials is that they are prone to misclassification of exposure status.

C.It is difficult to perform intention-to-treat analyses with randomized controlled trials.

D.Randomized controlled trials are observation studies because study arms are observed for outcomes.

E.Randomized controlled trials are not an effective study design for assessing rare outcomes.

1. 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.
2. Randomized clinical trial
3. case control study
4. retrospective cohort
5. Cross-sectional study
6. none of the above

3.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

4.Cohort Studies generally look at which of the following?

A.Determining the sensitivity and specificity of diagnostic methods

B.Identifying patient characteristics or risk factors associated with a disease or outcome

C.Variations among the clinical manifestations of patients with a disease

D.The impact of blinding or masking a study population

1. Which of the following is an 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.b and c

E.a, b, and c

6. What is the primary purpose of randomization:

A.To ensure that individuals in both the treatment and control groups actually take the drug that they are administered.

B.The biggest strength of the randomization in the experimental manipulation of the treatment of interest such that all other causes of disease are equally distributed between those who receive the treatment and those that does not. Thus, treatment will not be associated with any other risk factors for disease.

C.To ensure that the clinicians and study investigators are unaware of the exposure status of the individual in the study.

The following abstract summarize the results of epidemiologic studies.

Prevalence of headache among handheld cellular telephone users in Singapore: a community study.

Chia SE, Chia HP, Tan JS. Environ Health Perspect. 2000, 108(11):1059-62

We carried out a community study in Singapore to determine the prevalence of specific central nervous system (CNS) symptoms among hand-held cellular telephone (HP) users compared to nonusers and to study the association of risk factors and CNS symptoms among HP users. A total of 808 men and women between 12 and 70 years of age, who lived in one community, were selected using one-stage cluster random sampling and responses to a structured questionnaire. The prevalence of HP users was 44.8%. Headache was the most prevalent symptom among HP users compared to non-HP users, with prevalence rate ratio of 1.31 [95% confidence interval, 1.00-1.70]. There is a significant increase in the prevalence of headache with increasing duration of usage (in minutes per day). The use of HPs is not associated with a significant increase of CNS symptoms other than headache.

Note: the prevalence of headache among HP users was 60.3%.

For the abstracts:

1.Indicate the study design:

2.Indicate the "exposure/ risk factor" and the "disease/ outcome"

The following questions are based on the attached paper "Cancer and Tobacco Smoking" (Morton L. Levin, Hyman Goldstein, and Paul R. Gerhardt, JAMA, May 27, 1950, pages 336-338).

1. What study design has been employed.

A. case-control

B. Cohort (prospective)

C. retrospective cohort (or historical cohort)

D. ecologic

E. May be either a or c

2. In one or two sentences justify your choice.