Experiments Versus Case Studies

A frequently asked question is, “When should one choose to conduct a case

study, rather than an experiment?” To answer this question, it is important

to understand some basic differences between case-study methods and experimental

designs. Experiments allow the researcher to manipulate the independent

variables (those under the control of the experimenter) that are

being studied.

For example, in a study to determine the most effective treatment approach

for severe depression, subjects could be randomly assigned to one of

three different treatments. The treatments are under the control of the researcher

in the sense that he or she determines who will get a particular

treatment and exactly what it will be. On the other hand, case studies are

used in situations where the variables cannot be manipulated. Experiments

typically, although not exclusively, are performed in a laboratory setting.

Case studies occur in naturalistic settings, a research environment in which,

in contrast to laboratory research, subjects are studied in the environment

in which they live, with little or no intervention on the part of the researcher.

Experiments are characterized as having rigorous control over extraneous

variables. Case studies typically lack such control. Experiments

place a heavy emphasis on data-analysis procedures that use numbers and

statistical testing. Case studies emphasize direct observation and systematic

interviewing techniques, and they are communicated in a narrative form.

Experiments are designed so that they can be repeated. Case studies, by

their very nature, can be quite difficult to repeat.