Abstract
In this paper, we propose a control chart, called the “unit and group runs” (UGR) chart, which is useful to detect an increase in fraction nonconforming. The proposed chart starts with unit-level inspection and switches to the group-level inspection and back to the unit-level inspection according to a specified rule. The UGR chart gives a remarkable reduction in out-of-control average time to signal (ATS) as compared with the run-length CUSUM (Bourke (1991)), Bernoulli CUSUM (Reynolds and Stoumbos (1999)) and the synthetic control chart (Wu et al. (2001)). The proposed chart almost attains the lower bound for the out-of-control ATS and, hence, based on the ATS criterion, it is expected to outperform the other attribute-control charts. The steady-state performance of the proposed chart is also uniformly remarkable as compared with the other matched attribute-control charts. Therefore, the UGR chart for attributes enhances the effectiveness of statistical process control.
Additional information
Notes on contributors
M. P. Gadre
Mr. M. P. Gadre is Lecturer in Statistics at Mudhoji College. His email address is [email protected].
R. N. Rattihalli
Dr. R. N. Rattihalli is Professor and Head of the Department of Statistics. His email address is [email protected].