Multiple Control Groups
An observational study has multiple control groups if it has several distinct groups of subjects who did not receive the treatment. In a randomized experiment, every control is denied the treatment for the same reason, namely, the toss of a coin. In an observational study, there may be several distinct ways that the treatment is denied to a subject. If these several control groups have outcomes that differ substantially and significantly, then this cannot reflect an effect of the treatment, since no control subject received the treatment. It must reflect, instead, some form of bias.
Unable to display preview. Download preview PDF.
- Campbell, D. (1969). Prospective: Artifact and Control. In Artifact in Behavioral Research (eds., R. Rosenthal and R. Rosnow). New York: Academic Press, pp. 351–382.Google Scholar
- Campbell, D. and Boruch, R. (1975). Making the case for randomized assignment to treatments by considering the alternatives: Six ways in which quasi-experimental evaluations in compensatory education tend to underestimate effects. In: Evaluation and Experiment (eds., C. Bennett and A. Lumsdaine). New York: Academic Press, pp. 195–296.Google Scholar
- Campbell, D. and Stanley, J. (1963). Experimental and Quasi-Experimental Designs for Research. Chicago: Rand McNally.Google Scholar
- Lilienfeld, A., Chang, L., Thomas, D., and Levin, M. (1976). Rauwolfia derivatives and breast cancer. Johns Hopkins Medical Journal, 139, 41–50.Google Scholar
- Lilienfeld, A. and Lilienfeld, D. (1980). Foundations of Epidemiology (second edition). New York: Oxford University Press.Google Scholar
- Maclure, M. and Greenland, S. (1992). Tests for trend and dose-response: Misinterpretations and alternatives. American Journal of Epidemiology, 135, 96–104.Google Scholar
- Seltser, R. and Sartwell, P. (1965). The influence of occupational exposure to radiation on the mortality of American radiologists and other medical specialists. American Journal of Epidemiology, 81, 2–22.Google Scholar
- Solomon, R. (1949). An extension of control group design. Psychological Bulletin, 137–150.Google Scholar
- Weiss, N. (1981). Inferring causal relationships: Elaboration of the criterion of “doseresponse.” American Journal of Epidemiology, 113, 487–490.Google Scholar