Title: Effect of sampling intervals on economic design of proposed X-bar chart using Lorenzen-Vance cost model

Authors: D.R. Prajapati

Addresses: Department of Mechanical Engineering, PEC University of Technology, Chandigarh – 160012, India

Abstract: It is observed that sampling interval (h) and expected cost/hour (C) depend upon various parameters of economic design of proposed X-bar chart as well as in Lorenzen-Vance (1986) cost model. The proposed X-bar chart is based upon sum of chi-squares and has simplicity like Shewhart X-bar chart, but more efficient than standard X-bar chart. It is also as effective as CUSUM and EWMA charts for all the shifts in the process average. This paper deals with the effect of sampling intervals on economic design of proposed X-bar chart, using Lorenzen-Vance (1986) cost model. This comparison shows that the performance of proposed X-bar chart is very much comparable with X-bar chart proposed by McWilliams (1994) for sample sizes of five, six and seven, as the expected cost per hour (C) of proposed X-bar chart is very close to the expected cost per hour of McWilliams X-bar chart.

Keywords: X-bar charts; Thomas Lorenzen; Lonnie Vance; cost models; control limits; sampling intervals; expected costs; cost per hour; economic design; chi-squares; Walter Shewhart; CUSUM; cumulative sums; control charts; exponentially weighted moving average; EWMA; Thomas McWilliams; productivity; quality management.

DOI: 10.1504/IJPQM.2010.035895

International Journal of Productivity and Quality Management, 2010 Vol.6 No.4, pp.518 - 539

Available online: 07 Oct 2010 *

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