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A substantial bias in nonparametric tests for periodicity in geophysical data
Science (New York, N.Y.)
|November 13, 1987
Summary
A statistical test previously used to suggest periodic extinction rates is flawed. This method is biased and can produce artifactual 26-million-year periods due to data recording issues.
Area of Science:
- Paleontology
- Statistical Analysis
- Earth Science
Background:
- Previous studies suggested periodic mass extinctions with a 26-million-year cycle.
- Nonparametric statistical tests have been employed to analyze extinction rate periodicity.
Purpose of the Study:
- To critically evaluate a nonparametric test used for detecting periodic extinction rates.
- To investigate potential biases and artifactual results in extinction rate periodicity analyses.
Main Methods:
- Analysis of a specific nonparametric statistical test for periodicity.
- Simulation and examination of the test's sensitivity to measurement error, specifically the Signor-Lipps effect.
- Assessment of the impact of uneven temporal data spacing on statistical outcomes.
Main Results:
- The nonparametric test is substantially biased towards concluding a 26-million-year period, irrespective of the actual data.
- The test is highly sensitive to the Signor-Lipps effect, a common issue in fossil record data.
- Uneven time-series data can generate statistically significant but artificial periods of 26 million years.
Conclusions:
- The previously reported 26-million-year extinction periodicity is likely an artifact of the statistical method used.
- The employed test is unreliable for detecting true periodicities in extinction rates.
- Further research requires more robust statistical approaches to analyze extinction patterns.
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