Graficos de controle para media de um processo, com limites de advertencia e tamanhos amostrais variaveis

AUTOR(ES)
DATA DE PUBLICAÇÃO

1991

RESUMO

In this work we consider Shewhart s Classical Scheeme for the construction of X control charts, with parameters n0, k0 e h0 . In an atempt to improve its promptness to detect stable shifts on the process mean, we establish, in the region inside the control limits, a central stripe defined by a lower and an upper warning limit, such that, if one observation falls inside the control limits the next sample size will be np if it falls outside the warning limits and ng, otherwise, with ng >np. This new scheeme, which we call nV, is kept with the same basic costs as the reference Shehwart s scheeme, by choosing np , ng and the width of the central stripe such that E[n / X E (UCL,LCL)] = no, as long as the process is kept under control. We formally develop the basic statistical properties of this new scheeme, and show that it improves Shewhart s basic aproach in terms of the expected time between occurence and detection of the stable shift on the process average, in several situations of practical interest. The results are abundantly ilustrated thru Monte Carlo simulations

ASSUNTO(S)

tabelas etc estatistica - graficos

ACESSO AO ARTIGO

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