Types of epidemiological Studies

Broadly epidemiological studies may be classified into two broad types, depending upon the type of exposure:-

  • Observational (non-experimental) studies
  • Experimental studies

Observational studies

Observational studies allow nature to take its own course, the investigator observe, measure but does not intervene where the researcher has no control over the exposure. The observational studies, which comprise the majority of all epidemiological studies, are used when additional information is needed on a health problem or when the relationship between two or more variables need to be tested.

Experimental studies

The researcher controls the exposure. The experimental studies are useful to provide evidence of an association or the lack of association between an exposure and a health problem.

Other Classification:-

  • According to place of study
    • Laboratory study
    • Clinical study
    • Field trail/study
  • Method of data collection
    • Observational (non-experimental) study
    • Experimental study
  • According to the duration of study
    • Short duration – Cross-sectional study
    • Long duration – Longitudinal study
  • According to nature of characteristics of study
    • Case control study
    • Cohort study
  • According to nature of characteristics of study
    • Retrospective study
    • Prospective study

Descriptive vs analytical Epidemiology:

  • Control group: In descriptive study only one group is studied, no control group is required or used whereas in analytical study control group is used
  • Relation between exposure and outcome (cause & effect): Descriptive study does not correlate or cannot establish relationship between exposure and outcome (cause & effect) whereas analytical study does.
  • Hypothesis: Descriptive study generate hypothesis for association between risk factor and illness; whereas analytical study used to test specific etiological hypothesis.

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