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. Author manuscript; available in PMC: 2015 Apr 30.
Published in final edited form as: J Investig Med. 2009 Dec;57(8):818–824. doi: 10.231/JIM.0b013e3181c2996c

Table 3.

Definitions for statistical hypothesis testing

  • A Type I error (alpha) is the risk of inferring a difference between study groups when there is no such difference.

  • A Type II error (beta) is the risk of inferring no difference between study groups when there is such a difference.

  • Power is the statistical test’s ability to detect a true difference. Power = 1 - Type II error.