Design of quasi-experiments
A quasi-experiment is an experiment in which the subjects to be observed are not randomly assigned to different groups in order to measure outcomes, as in a true experiment, but grouped according to a characteristic that they already possess.[1]
For example, a quasi-experiment to measure the effects of living in a single- or two-parent home on children's response to different forms of advertising would group the children by whether they live in a single- or two-parent home, show them some sample ads, and measure the correlation between how they respond to the ads and the number of parents in their home. A true experiment would randomly assign children at birth to single- or two-parent homes in order to control for all other variables. Quasi-experiments are commonly used in the social sciences, where often it's not practical or ethical to set up the independent variable as in a true experiment.
The disadvantage of quasi-experiments is that they are more open to confounding variables. In the example above, a variation in the children's response to the ads might not result from the number of parents in their home, but from factors that might have merely a temporary correlation with the number of parents in their home: cultural background, language spoken at home, parents' income level, or perhaps factors that we don't even know about.
References
- ^ Rossi, Peter Henry (2004). Evaluation: A Systematic Approach, 7th Ed. SAGE. p. 237. ISBN 978-0761908944.
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External links
- Quasi-Experimental Design at the Research Methods Knowledge Base