CLIO Learning Modules
Study DesignSelectionSample SizeData Collection and AnalysisHuman Subjects

'Me too studies'
Target Population
Attributable Risk
Relative Risk
Data Sources
Study Time
Case Control
Nested Case-Control
Prospective Cohort
Retrospective Cohort
Randomized Clinical Trial
Target Population

The target population of your study is the population for which your conclusions are meant to be valid.


Venn diagram of target, sample, and study populations

The target population is the broadest category for which you wish to extend your conclusions. For the sake of expediency and efficiency, you will conduct your study within a more restricted population — your study population. From your study population, a sample will be drawn, which will be the subjects of your study, though in certain situations, it may be feasible to include the entire study population.


Hypothesis: Daily consumption of soy sauce by Chinese Americans causes gastric cancer.

Your target population is Chinese Americans. Suppose that you are located in San Francisco, CA, and it is not feasible for you to conduct a national study. A practical study population would be Chinese Americans living in San Francisco. To obtain subjects for your study, you might choose to random-digit dial (RDD) using the telephone prefixes used in San Francisco’s Chinatown. By selecting your study and sample populations in this manner, the conclusions of your study can be reasonably generalized to the target population of all Chinese Americans.

Venn diagram of example study population


Defining your target population is an important step in study design — it will guide you as you as develop procedures and methods for selecting your study participants. With each step, the objective is to retain the ability to generalize the findings from your sample to your target population.

Further reading

eBMJ - What is epidemiology?

June 4, 2004 v0.20
Copyright © 2004 Stanford School of Medicine