A number-between-events control chart for monitoring nite horizon production processes
Résumé
In this paper, we present a number-between-events (NBE) control chart for monitoring the fraction nonconforming in nite horizon production (FHP) processes and related specic performance measures. When monitoring fractions nonconforming in FHP processes, the common binomial p-chart has two crucial limitations: the underlying distributional assumptions are violated when dealing with low-volume production and a scarce eciency in the case of processes characterized by a low fraction nonconforming. Thus, an ecient monitoring of FHP processes requires the selection of the correct underlying statistical model: in this case, a distribution from the hypergeometric family of discrete statistical distributions. An ecient statistical monitoring of processes with low fractions nonconforming can be achieved by means of discrete time-between-events (TBE) control charts, which count the number of units up to the appearance of a xed number of nonconforming units in the sample. Here, we present a discrete TBE-chart, denoted as NBE-chart, based on the negative hypergeometric distribution that meets numerous requirements of ecient monitoring of FHP processes. The proposed control chart can be conveniently used for both low-volume and mass production in processes with frequent changeovers.
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