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January 17, 2007

Estimating Treatment Effects Using Observational Data

Author Affiliations

Author Affiliations: Department of Biostatistical Sciences, Wake Forest University School of Medicine, Winston Salem, NC (Dr D’Agostino, Jr); and Department of Mathematics and Statistics, Boston University, and Harvard Clinical Research Institute, Boston, Mass (Dr D’Agostino, Sr).

JAMA. 2007;297(3):314-316. doi:10.1001/jama.297.3.314

The randomized clinical trial (RCT) is the ideal method for measuring treatment effects. Participants in clinical trials are randomly assigned to a treatment or control group. Randomization reduces biases by making treatment and control groups “equal with respect to all features,” except the treatment assignment. When randomization is performed correctly, differences in efficacy found by statistical comparisons can be attributed to the difference between the treatment and control.1

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