X charts with supplementary samples to control the mean and variance

Nenhuma Miniatura disponível

Data

2000-11-10

Título da Revista

ISSN da Revista

Título de Volume

Editor

Taylor & Francis Ltd

Resumo

A standard X chart for controlling a process takes regular individual observations, for instance every half hour. This article proposes a modification of the X chart that allows one to take supplementary samples. The supplementary sample is taken (and the (X) over bar and R values computed) when the current value of X falls outside the control limits. With the supplementary sample, the signal of out-of-control is given by an (X) over bar value outside the (X) over bar chart's control limits or an R value outside the R chart's control limit. The proposed chart is designed to hold the supplementary sample frequency, during the in-control period, as low as 5% or less. In this context, the practitioner might prefer to verify an out-of-control condition by simply comparing the (X) over bar and R values with the control limits. In other words, without plotting the (X) over bar and R points. The X chart with supplementary samples has two major advantages when compared with the standard (X) over bar and A charts: (a) the user will be plotting X values instead of (X) over bar and R values; (b) the shifts in the process mean and/or changes in the process variance are detected faster.

Descrição

Palavras-chave

Como citar

International Journal of Production Research. London: Taylor & Francis Ltd, v. 38, n. 16, p. 3801-3809, 2000.

Coleções