Health Services Research (HSR) Methods
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Time Series Design
Synonyms: Longitudinal Study

A quasi-experimental research design in which periodic measurements are made on a defined group of individuals both before and after implementation of an intervention.

Time series studies are often conducted for the purpose of determining the intervention or treatment effect.


To examine the effect of a new, government-funded meal program on school children, a nutritional scale is administered to a sample of school children receiving this program. The nutritional scale is measured once before the program, and then 3 months after the program, and at the end of one year following program implementation. The outcomes at different time points are compared to assess the program effect.

Further Reading
Gliner, J.A. and G.A. Morgan. 2000. Research Methods in Applied Settings, Mahwah, NJ: Lawrence Erlbaum Associates.

Marczyk, G.R. et al. 2005. Essentials of Research Design and Methodology, Hoboken, NJ: John Wiley & Sons.

Campbell, D. and J. Stanley. 1963. Experimental and Quasi-Experimental Designs for Research, Boston, MA: Houghton Mifflin Company.