Misuse of the 'modified' t statistic in regulatory telecommunications

Since the enactment of the Telecommunications Act of 1996 (1996), extensive expert testimony has justified use of the 'modified' t statistic (Brownie et al. Biometrics 46 (1990) 259-266) for performing two-sample hypothesis tests on Bell companies' CLEC and ILEC performance measurement data. This paper demonstrates how key statistical claims made about the 'modified' t in this setting are false, leading not only to incorrect inferences as it currently is being used, but also to the possible undermining of the primary stated objective of the Act--the promotion of competition in the newly deregulated local telephone service markets. A simulation study provides strong evidence for the use of several other easily-implemented statistical procedures in this context; they should be useful in other settings as well.