Home

Pearls

More
Features     

More
Reviews     

Opportunities

Editor in Chief    

Order
Form

Site Map

Contact Me 

A.  Study Design and Terminology

1. Cohort study: refers to the group of subjects who are followed forward in time to see which ones develop the outcome.

	Prospective cohort study:  follows subjects from presentfuture
	Retrospective cohort study:  follows subjects from pastpresent
	Nested cohort study:  Retrospective + Prospective study

	Cohort studies provide incidence--rate of development of a disease over a period of time.
	May give predictive factors of a condition.
	Expensive and impractical for rare diseases.
	Sensitive to confounding variables.

2. Case-Control (retrospective) study: a group of people who have a disease (cases) are compared with people whom they closely resemble except for the presence of the disease under study controls.

	Follows subjects from presentpast
	Provides odds ratio:  strength of association among predictors in the cases and in the controls.
	Sample sizes can be very small
	Applicable for finding exposures of disease and studies of rare diseases.

3. Cross-Sectional studies: exposure and outcome are measured at the same point in time.

	Provides prevalence and relative prevalence
	Cannot provide casual relationship:  only associations
	Design is time and cost efficient

4. Clinical trials: prospective studies in which an intervention is applied.
5. Meta-analysis: retrospective analysis of studies regard to the same topic.
6. P-value:  likelihood of the results by chance (needs to be <= 0.05 to be considered significant).

Top of Page   Return to Features Page