Publication Date:
2016-09-02
Description:
Statistical issues arising in the certification phase of class action cases are illustrated by examining the data on promotion to the Management Trainee position in Dukes v. Wal-Mart II . After reviewing problems in the analyses submitted to the court by both parties, an alternative approach is presented. The high p -value of the analogue of the Breslow–Day homogeneity test suggests that the observed variability of the district-wide odds ratios of female to male promotions may result from random variation about a common odds ratio. The additional fact that 40 of 42 districts in California state had odds ratios less than one and that the two largest odds ratios barely exceeded one (1.081 and 1.118) justify a proper aggregation of the district level data in each region and ultimately a state-wide analysis. The estimated common odds ratio of 0.475 demonstrates that the data for all the districts in California state are consistent with a system in which women had about half the odds of being promoted than men. In addition, our analysis shows that even when there is a common pattern of a female disadvantage, there will be substantial variation in the differences between the observed and expected female shares of promotions in the individual districts due to random fluctuation. Neither party examined the data for homogeneity or applied an appropriate combination test, the court required that for plaintiffs to establish a common pattern, statistical significance needs to occur in at least one-half of districts of a region. A power analysis, not submitted to the court, indicates that this requirement is far too stringent.
Print ISSN:
1470-8396
Electronic ISSN:
1470-840X
Topics:
Mathematics
,
Law
