The robustness of two popular process capability ratios, C p and C p ., when the random process being observed departs from normality is analysed. The distributions of estimated processcapability ratios are derived and used as a basis for validation of large-scale simulation studies in an examination of departures from normality. The simulation studies and analytical results provide a basis for recommended procedures. It is recommended that the impact of process distributions be considered before using popular processcapability indexes, due to the lack of robustnesswhendepartures from normalityare ecountered. Asan extension of our findings, weconsiderthe Taguchi lossfunctionas a generalization to process capability analysis regardless of the underlying population distribution.
This paper describes the results of an effort to predict future freight volume in the truckload (TL) trucking industry. The approach involves the use of stepwise multiple linear regression models that relate freight volume to a variety of economic indicators. The models are built using a large set of actual freight data provided by J.B. Hunt Transport (JBHT), one of the world’s largest TL carriers. The data was first analyzed using the overall set of national data, and then for specific industrial and regional segments. The overall results of these analyses should prove useful to a wide variety of transportation and logistics operations.
SUMMARY A double-blind cross-over trial between pheneturide and phenytoin in ninety-four outpatients with epilepsy is described. There was no significant difference between the frequency of seizures in the two groups. The difficulties in comparing two anticonvulsants of similar efficacy are discussed particularly in relation to ethical problems, the selection of patients and trial design.Recent research in anticonvulsant drugs has concentrated on their mode of action, their absorption, metabolism and elimination. Thus while the pharmacokinetics of these drugs are well understood, there are few adequate trials to test their efficacy in the management of epilepsy,' 2 possibly because ethical and design difficulties frequently
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