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Science 13 November 1987:
Vol. 238. no. 4829, pp. 940 - 945
DOI: 10.1126/science.238.4829.940
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Articles

A Substantial Bias in Nonparametric Tests for Periodicity in Geophysical Data

STEPHEN M. STIGLER 1 and MELISSA J. WAGNER 1

1 Department of Statistics, University of Chicago, Chicago, IL 60637.

A nonparametric test that has been used to conclude that extinction rates are periodic with a period of 26 million years is shown to be substantially biased toward this conclusion, regardless of whether or not the data are periodic in origin (and, indeed, regardless of the actual period if they are in fact periodic). The test is shown to be sensitive to measurement error of a type expected with these data (early recording of extinctions due to missing fossil specimens, the "Signor-Lipps effect"), and it is shown that because of the unequal spacing in time, such models may be expected to produce statistically significant but artifactual periods of (in this case) exactly 26 million years over the span of time actually used.

Submitted on April 16, 1987
Accepted on August 6, 1987


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Orbital forcing timescales: an introduction.
M. R. House (1995)
Geological Society, London, Special Publications 85, 1-18
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Periodicity in extinction and the problem of catastrophism in the history of life.
J. J. SEPKOSKI JR. (1989)
Journal of the Geological Society 146, 7-19
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Testing for Periodicity of Extinction.
D. M. Raup, D. M. RAUP, and J. J. SEPKOSKI JR. (1988)
Science 241, 94-96
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Response: Testing for Periodicity of Extinction.
S. M. STIGLER and M. J. WAGNER (1988)
Science 241, 96-99
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Abrupt Climate Change and Extinction Events in Earth History.
T. J. Crowley, T. J. Crowley, and G. R. North (1988)
Science 240, 996-1002
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