The control of industrial processes subject to trends in quality
成果类型：
Article
署名作者：
Tippett, LHC
刊物名称：
BIOMETRIKA
ISSN/ISSBN：
0006-3444
发表日期：
1944
页码：
163172
关键词：
摘要：
In order to decide when to discard a tool, which is used in manufacturing an article which should meet specifications, one procedure is to take samples at regular intervals of time, measure the articles, and calculate the mean dimension for the samples and discard the tool when the mean reaches a certain value. The sample means are subject to sampling errors so that they do not measure exactly the true or population mean of all the articles produced at a given time. If the tools are discarded at one level of sample means, some will be discarded before the population mean has reached that level and others afterwards. There will be a frequency distribution of states of wear, as measured by the population mean, at which different tools are discarded. It is the purpose of this paper to determine that frequency distribution and discuss the practical consequences. The results may be applied generally to any process having a trend in some characteristic that is estimated at regular intervals by any measure having a sampling error. Tables are given containing the probabilities of time of discard of tools being later than specified times. Applications are given which show the use '' of these tables.