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.