Law, Probability and Risk - current issue

Issues in the use of survival analysis to estimate damages in equal employment cases

Pan, Q., Gastwirth, J. L. — 2009-04-17

After plaintiffs prevail in employment discrimination cases, courts need to estimate the compensation they deserve. This issue arose after a defendant was found to have discriminated against job applicants older than 40 years. In order to compensate the successful plaintiffs, the court needed to estimate the length of time they would have worked, had they been hired. The job histories of 127 current employees and 43 employees who recently left were available for analysis. The accelerated failure time model, commonly used for the analysis of survival data, provides an estimate of the mean employment duration, adjusting for covariates. Three legal opinions emphasized that damage awards should be based on data concerning employees with similar qualifications as the plaintiffs so an ability model is proposed. A simulation study illustrates the potential underestimation of the job tenures of the deserving plaintiffs by the method adopted in the case. On the other hand, that method, which did not consider ability, can lead to compensating low-ability plaintiffs who would not be hired even in a non-discriminatory environment. Finally, the methods are applied to the motivating example and an appropriate damage award is suggested.

The effect of dependence between observations on the proper interpretation of statistical evidence

Gel, Y. R., Miao, W., Gastwirth, J. L. — 2009-04-17

In a recent securities law case, the statistical methods used by the regulator in analysing data on daily commissions and hypothetical profits from initial public offerings (IPOs) assumed that the data on consecutive days were independent. Consecutive observations in most business and economic data, however, are positively correlated. While statistical articles demonstrate that this type of dependence affects the distribution of virtually all statistics, including non-parametric and goodness-of-fit tests, the magnitude of the effect may not be fully appreciated. For example, in one comparison of commissions one broker received on days with an IPO to the days when no IPO was issued yielded a statistically significant p-value of 0.02, under the independence assumption. Accounting for serial correlation, the test actually had a non-significant p-value close to 0.09. Other examples of the effect of dependence include jury discrimination cases in locales where grand jurors can serve two consecutive terms as well as cases concerned with environmental pollution where measurements are spatially and temporally correlated. This paper describes the noticeable effect violations of the independence assumption can have on statistical inferences. The methods for correcting some standard non-parametric tests for serial correlation are also discussed.

Liability for negligently increased risk: the repercussions of Barker v. Corus UK (plc)

Miller, C. — 2009-04-17

The philosophical problem of ‘references classes’ is discussed within the context of probabilistic causation and, more particularly, liability for the negligent increase of the risk of personal injury. The implications of a recent addition to the U.K. case law on asbestos-related disease are then examined.

Forensic identification and criminal justice: forensic science, justice and risk, by Carole McCartney

Roth, A. L., Ungvarsky, E. J. — 2009-04-17

Clarification and corrections to 'On the attribution of probabilities to the causes of disease' by Peter Cooke and Arianna Cowling (Law, Probability and Risk (2005), 4, 251-256)

Cooke, P. — 2009-04-17