For example, looking at the incidence of lung cancer in smokers versus nonsmokers, or comparing the antenatal dietary habits of mothers with normal and low-birth babies.
The researcher does not do any active intervention in any individual, and the exposure has already been decided naturally or by some other factor. Observational studies are those where the researcher is documenting a naturally occurring relationship between the exposure and the outcome that he/she is studying. Observational versus interventional (or experimental) studies If a drug had been started in some individuals but not in the others, before the study started, this counts as exposure, and not as intervention – since the drug was not started specifically for the study. Typically, the term “exposure” is used when the “causative” variable is naturally determined (as in observational studies – examples include age, sex, smoking, and educational status), and the term “intervention” is preferred where the researcher assigns some or all participants to receive a particular treatment for the purpose of the study (experimental studies – e.g., administration of a drug). The outcome (or predicted or dependent) variable develops as a consequence of the exposure (or intervention). It is also referred to as the independent or the predictor variable. Exposure (or intervention) refers to the risk factor whose effect is being studied. Here, the question is whether one variable is associated with or responsible for change in the value of the other variable. Exposure (or intervention) and outcome variablesĪ large proportion of research studies assess the relationship between two variables.
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