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Beta (β)

    What is Beta (β)?

    • The probability of saying or concluding that a study found no difference between groups when in reality there is a difference.
    • This is also known as the chance of making a type II error or false negative rate.
    • β ("Beta") is an important part of power, which is defined as being 1 - β.
    • Most clinicians accept a power of 0.8 (or 80%), which means β has to be 0.2 (or 20%)
    • Reducing β will decrease the chance of making a type I error and at the same time increase the power of the study.
      • Note:  As β is decreased, the sample size will increase in order to find a difference if one exists. This will clearly add to the cost and time to complete a study.
    Editors & Reviewers

    Editors & Reviewers:

    • Anthony J. Busti, MD, PharmD, FNLA, FAHA

    Last Reviewed:  July 2015