So i'm working on a Greenhouse-Geisser correction and i found this "John, Nagao & Sugiura’s test for sphericity" in this publication (https://www.utdallas.edu/~herve/abdi-GreenhouseGeisser2010-pretty.pdf).

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Could it be that they calculated the value of the chi square distribution wrong? After Equation 20 they calculate the probability p=0.004, but when i use scipy, i get p=0.0004. So i'm confused if i did not understand the process right or if there is an error(my guess).

  • 2
    $\begingroup$ It's a typographical error: they omitted a "0" in the expression of the p-value. $\endgroup$
    – whuber
    Sep 18, 2018 at 14:16
  • $\begingroup$ Exactly as i thought. Thanks for the second opinion! $\endgroup$
    – T.Tos
    Sep 18, 2018 at 15:39

1 Answer 1


Yes, the numbers they give produce a p-value of 0.000402. They probably made a typo in their publication.

The site I used to compute the p-value.


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