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Appendix 07: Critical Values for Grubb’s Test

  • Page ID
    6643
  • The following table provides critical values for G(α, n), where α is the probability of incorrectly rejecting the suspected outlier and n is the number of samples in the data set. There are several versions of Grubb’s Test, each of which calculates a value for Gij where i is the number of suspected outliers on one end of the data set and j is the number of suspected outliers on the opposite end of the data set. The values given here are for G10, where

    \[G_\ce{exp} = G_{10} = \dfrac{|X_\ce{out} - \overline{X}|}{s}\]

    The suspected outlier is rejected if Gexp is greater than G(α, n).

    G(α, n) for Grubb’s Test of a Single Outlier
    α⇒ 0.05 0.01
    n
    3 1.155 1.155
    4 1.481 1.496
    5 1.715 1.764
    6 1.887 1.973
    7 2.202 2.139
    8 2.126 2.274
    9 2.215 2.387
    10 2.290 2.482
    11 2.355 2.564
    12 2.412 2.636
    13 2.462 2.699
    14 2.507 2.755
    15 2.549 2.755