Law, Probability and Risk Advance Access originally published online on August 13, 2007
Law, Probability and Risk 2008 7(1):61-74; doi:10.1093/lpr/mgm013
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© The Author [2007]. Published by Oxford University Press. All rights reserved.
Case comment: an expert's report criticizing plaintiff's failure to account for multiple comparisons is deemed admissible in EEOC v.Autozone*
Department of Statistics, George Washington University Washington, DC, 20052, USA
jlgast{at}gwu.edu
Received on 5 April 2007. Revised on 25 April 2007. Accepted on 2 May 2007.
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Abstract |
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In its opinions in Daubert, Joiner and Kumho Tire, the U.S. Supreme Court assigned trial judges a ‘gate-keeping’ role in assuring that proposed expert testimony is sufficiently reliable that it should be admitted into evidence. A section of the Daubert decision described guidelines to assist trial judges in their evaluation of expert testimony. This comment discusses a careful district court opinion concerning a motion, under the principles of Daubert, to exclude the report of defendant's expert in the sex discrimination case, EEOC v. Autozone. The technical statistical issue dealt with the need for adjusting the observed significance levels or p-values of individual statistical tests when a large number of related tests are conducted. The Equal Employment Opportunity Commission and its expert argued that while such adjustments are used in medical applications of statistics, they are not needed in labour economics. The decision is noteworthy because the judge realized that the principles of statistical inference remain the same regardless of the origin of the data. After describing the issue and reanalysing some of the data, alternative statistical methods that stratify the data into comparable subgroups and combine the results for the separate strata are often more appropriate. They avoid making many separate tests and have higher statistical power to detect discrimination. Since 10 years of hiring and promotion data were analysed, which cover both pre- and post-charge time periods, two possible scenarios are described. The first is the one that apparently was the focus of both experts and the second focuses on the status of a particular female plaintiff for a job as guard in the early period. It is shown that overall the data do not support a claim of class-wide discrimination but might support a claim of sex discrimination in hiring for guard positions in the pre-charge time period.
Keywords: admissibility of expert testimony; combination methods; Daubert criteria; examining pre- and post-charge data; multiple comparisons; principles of statistical inference