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Experimental study designs are the primary method for testing the effectiveness of new therapies and other interventions, including innovative drugs. By the 1930s, the pharmaceutical industry had adopted experimental methods and other research designs to develop and screen new compounds, improve production outputs, and test drugs for therapeutic benefits. The full potential of experimental methods in drug research was realized in the 1940s and 1950s with the growth in scientific knowledge and industrial technology.1

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In the 1960s, the controlled clinical trial, in which a group of patients receiving an experimental drug is compared with another group receiving a control drug or no treatment, became the standard for doing pharmaceutical research and measuring the therapeutic benefits of new drugs.1 By the same time, the double-blind strategy of drug testing, in which both the patients and the researcher are unaware of which treatment is being taken by whom, had been adopted to limit the effect of external influences on the true pharmacological action of the drug. The drug regulations of the 1960s also reinforced the importance of controlled clinical trials by requiring that proof of effectiveness for new drugs be made through use of these research methods.2,3

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In pharmacoepidemiology, the primary use of experimental design is in performing clinical trials, most notably randomized, controlled clinical trials.4 These studies involve people as the units of analysis. A variation on this experimental design is the community intervention study, in which groups of people, such as whole communities, are the unit of analysis. Key aspects of the clinical and community intervention trial designs are randomization, blinding, intention-to-treat analysis, and sample size determination.

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An experiment is a study designed to compare benefits of an intervention with standard treatments, or no treatment, such as a new drug therapy or prevention program, or to show cause and effect (see Figure 3-2). This type of study is performed prospectively. Subjects are selected from a study population, assigned to the various study groups, and monitored over time to determine the outcomes that occur and are produced by the new drug therapy, treatment, or intervention.

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Experimental designs have numerous advantages compared with other epidemiological methods. Randomization, when used, tends to balance confounding variables across the various study groups, especially variables that might be associated with changes in the disease state or the outcome of the intervention under study. Detailed information and data are collected at the beginning of an experimental study to develop a baseline; this same type of information also is collected at specified follow-up periods throughout the study. The investigators have control over variables such as the dose or degree of intervention. The blinding process reduces distortion in assessment. And, of great value, and not possible with other methods, is the testing of hypotheses. Most important, this design is the only real test of cause–effect relationships.

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The disadvantages of experimental design involve subject participation criteria ...

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