Comments on "Control-limits of QC charts for skewed distributions using weighted-variance

The commenter offers three criticisms of the suggested weighted variance (WV) method in the paper by Choobineh and Ballard (ibid., vol.R-36, p.473-7, Oct. 1987), although agreeing that the method, which introduces different factors for the upper and lower control limit in the case of a skewed distribution, is generally simple and sensible. He contends that: (1) the WV method does not use the same kind of dispersion measure as Shewhart control charts do, as claimed; (2) an example given is not well put; and (3) the WV method is heuristic, as claimed by the authors, so it is not the unique solution to an exactly described problem.<>