Study Designs

Question 0

multi-group comparison studies

Answer 0

ecological studies that test associations between average exposure levels and overall outcome rates among several groups; data sometimes comes from secondary sources

Question 1

exploratory studies

Answer 1

descriptive ecological studies that look at variations in outcomes across ecological units; exposure is not assessed

Question 2

time-trend studies

Answer 2

ecological studies AKA time-series studies; they detect changes in the average exposure level and outcome rates for a single population over time

Question 3

mixed studies

Answer 3

examine changes in average exposure level and outcome rates for several populations over time; think of mixed studies as a combination of multiple-group comparison and time-trend studies

Question 4

unit of analysis

Answer 4

that which is being studied; usually the individual

Question 5

cross-sectional studies

Answer 5

assess both exposure and outcome status at the same point in time or during a brief period of time; it is difficult to distinguish between exposure and outcome since they are assessed at the same time; prevalence is the usual measure of disease frequency in cross-sectional studies

Question 6

descriptive cross-sectional study

Answer 6

a study designed to uncover patterns of distribution by person, place, or time variables that may suggest hypotheses for further study; sometimes only exposure or only outcome is assessed

Question 7

case-control studies

Answer 7

classifies subjects by outcome status; only new cases of disease are included in the study and past exposures are assessed (this maintains appropriate temporal sequence between the two); no need for follow-up

Question 8

prospective cohort studies

Answer 8

classify subjects without the outcome of interest on the basis of exposure status (PCSs start with exposure…opposite of case-control studies); take longer time due to follow-up periods

Question 9

Case report/ case series

Answer 9

They describe the experience of a patient or group of patients, which may lead to a new hypothesis.

Case report: careful and detailed report by one of more clinicians of the clinical profile of a single patient.

Question 10

Strengths of Case Reports

Answer 10

• Document unusual medical history/clinical features of disease
• Can provide clues in the identification of a new disease or adverse effects of exposures

Question 11

Weaknesses of Case Reports

Answer 11

• There is nothing with which to compare the data
• Cannot be used to test for presence of a valid statistical association
• 1 clue is no sufficient data

Question 12

Case Series

Answer 12

Collections of individual case reports, usually within a fairly short period of time; description of clinical/epidemiological characteristics of a number of patients with a given disease