EPID 309 Study Designs
Cross-Sectional Study - answer observational in nature and give a snapshot of the
characteristics of study subjects in a single point of time. Simple to conduct. Used to
assess the prevalence of a disease in a population.
Ecologic study - answer used when data at an individual level is unavailable or when
large-scale comparisons are needed to study the population-level effect of exposures
on a disease condition. Applicable only at the population level.
Case-control study - answer used to determine the degree of associations between
various risk factors and outcomes. The factors that affect the risk of a disease are called
exposures. Researchers look in the past for the possible exposures these patients
might have had to a risk factor.
Cohort study - answer classify patients into two groups based on their exposure status.
They are followed over time to see who develops the disease in the exposed and non-
exposed groups.
Use Relative Risk for measure of effect
Clinical trial - answerthe researcher randomly assigns the subjects to a control group
and an experimental group. Randomization avoids confounding and minimizes selection
bias. This enables the researcher to have similar experimental and control groups
thereby enabling them to isolate the effect of an intervention.
Community Intervention - answerintervention designed for the purpose of educational
and behavioral changes at the population level
Case Report/Case Series - answerMost often used to report rare occurrences.
Not statistically valid.
Considered a source of anecdotal evidence.
Cross-Sectional Study - answer observational in nature and give a snapshot of the
characteristics of study subjects in a single point of time. Simple to conduct. Used to
assess the prevalence of a disease in a population.
Ecologic study - answer used when data at an individual level is unavailable or when
large-scale comparisons are needed to study the population-level effect of exposures
on a disease condition. Applicable only at the population level.
Case-control study - answer used to determine the degree of associations between
various risk factors and outcomes. The factors that affect the risk of a disease are called
exposures. Researchers look in the past for the possible exposures these patients
might have had to a risk factor.
Cohort study - answer classify patients into two groups based on their exposure status.
They are followed over time to see who develops the disease in the exposed and non-
exposed groups.
Use Relative Risk for measure of effect
Clinical trial - answerthe researcher randomly assigns the subjects to a control group
and an experimental group. Randomization avoids confounding and minimizes selection
bias. This enables the researcher to have similar experimental and control groups
thereby enabling them to isolate the effect of an intervention.
Community Intervention - answerintervention designed for the purpose of educational
and behavioral changes at the population level
Case Report/Case Series - answerMost often used to report rare occurrences.
Not statistically valid.
Considered a source of anecdotal evidence.
