General Considerations in Clinical Research Design


Learning Objectives

  1. 1.

    The study population refers to all people who enter a study.

  2. 2.
    Common exclusion criteria in clinical studies include:
    1. a.

      Exclusion of people who have prevalent disease to focus on incident outcomes.

    2. b.

      Exclusion of people who have major disease risk factors to focus on the exposure of interest.

    3. c.

      Exclusion of people whose disease development may be missed in the study.

  3. 3.

    The choice of study population influences the generalizability of study findings.

  4. 4.

    The exposure is a factor that may explain or predict the presence of an outcome.

  5. 5.

    The outcome is a factor that is being explained or predicted in the study.

  6. 6.

    Observational studies observe the exposure; interventional studies assign the exposure.

  7. 7.
    Several factors favor causal inference in epidemiology research:
    1. a.

      Randomized evidence

    2. b.

      Strong associations

    3. c.

      Temporal relationship

    4. d.

      Exposure-varying response

    5. e.

      Biological plausibility


This chapter presents fundamental elements of a clinical/epidemiological research study: the study population, exposure, outcome, and the general study design. Specific study designs, along with their inherent strengths and weaknesses, are discussed in subsequent chapters. The chapter concludes with a discussion of factors that favor causal inference.


Bladder Cancer Sudden Infant Death Syndrome Biological Plausibility Streptococcal Infection Pneumococcal Pneumonia 
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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.University of WashingtonSeattleUSA

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