Designs of control charts with optimal manpower deployment

This article proposes an algorithm for managing and deploying manpower (equipped with adequate measuring instrument) to a statistical process control (SPC) scheme so that the resultant control chart (referred to as M-chart) minimizes the expected total cost Ctotal incurred in the implementation of SPC. Unlike in the economic chart designs, most input specifications required by the design of an M-chart can be easily determined by practitioners. The design of an M-chart also takes into account the probability distribution of the random process shifts. The results of an example and a comprehensive study show that the M-chart can reduce the total cost by about 66%, on average, compared with the conventional control charts. It is also found that, in most SPC schemes, the allocated manpower is far less than needed and, consequently, the total cost can be significantly reduced by making some managerial arrangement to increase SPC manpower. Some useful guidelines are provided in this article to aid the management and determination of the appropriate amount of manpower for a particular application. Even though the M-chart is discussed in detail only for the chart detecting mean shifts, the general idea can be applied to many other charts (e.g. the CUSUM and EWMA charts) and to monitoring both process mean and variance.