Scopul nostru este sprijinirea şi promovarea cercetării ştiinţifice şi facilitarea comunicării între cercetătorii români din întreaga lume.
Autori: Tadikamalla, Pandu, Banciu, Mihai, and Popescu, Dana
Editorial: Naval Research Logistics, 55(1), p.91-99, 2008.
The distribution of the range of a sample, even in the case of a normal distribution, is not symmetric. Shewhart’s control chart for range and other approximations for range from skewed distributions and long-tailed (leptokurtic) symmetrical distributions assume the distribution of range as symmetric and provide 3 sigma control limits. We provide accurate approximations for the R-chart control limits for the leptokurtic symmetrical distributions, using a range quantile approximation (RQA) method and illustrate the use of the RQA method with a numerical example. As special cases, we provide constants for the R-chart for the normal, logistic, and Laplace distributions.
Cuvinte cheie: range control charts, long-tailed distributions, normal distribution, logistic distribution, Laplace distribution, Shewhart method, statistical quality control