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Randomized Trials

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Epidemiology and Biostatistics

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Learning Objectives

  1. 1.

    Randomized trials should be considered when:

    1. a.

      There is uncertainty regarding the effect of an exposure or treatment

    2. b.

      The exposure can be modified in a trial setting

  2. 2.

    Phase I and phase II studies evaluate the tolerability and biological activity of a drug; phase III and phase IV studies are randomized trials that evaluate clinical endpoints.

  3. 3.

    Potential limitations of randomized trials include:

    1. a.

      Limited generalizability of the study population

    2. b.

      Limited generalizability of the study environment

    3. c.

      Randomized trials address a narrow study question

    4. d.

      Randomized design accounts only for confounding

  4. 4.

    Common measures of effect in randomized trials are relative risk and risk difference.

  5. 5.

    The number needed to treat or harm = 1/risk difference.

  6. 6.

    The intention-to-treat analysis predictably leads to bias toward the null.

  7. 7.

    Criteria used to judge whether results of a subgroup analysis are valid include:

    1. a.

      Biological plausibility for a particularly strong effect in the subgroup

    2. b.

      The subgroup analysis was pre-specified

    3. c.

      Reasonably large number of outcomes in the subgroup

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Author information

Authors and Affiliations

  1. University of Washington, Seattle, WA, USA

    Bryan Kestenbaum

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  1. Bryan Kestenbaum
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Correspondence to Bryan Kestenbaum .

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© 2009 Springer Science+Business Media, LLC

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Kestenbaum, B. (2009). Randomized Trials. In: Epidemiology and Biostatistics. Springer, New York, NY. https://doi.org/10.1007/978-0-387-88433-2_7

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  • DOI: https://doi.org/10.1007/978-0-387-88433-2_7

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  • Publisher Name: Springer, New York, NY

  • Print ISBN: 978-0-387-88432-5

  • Online ISBN: 978-0-387-88433-2

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