Steiner has presented a CS (Confirmation Sample) &Xmacr;chart to detect more sensitively small or moderate shifts in the process mean from the in-control state on the Shewhart &Xmacr; chart. In the case that in-control values for the process mean and variance, μand σ2, are unknown, these unknown parameter values are estimated from some m initial subgroups of size n taken when the process is believed to be stable. When the centerline and control limits of the CS&Xmacr;chart are set up by using these estimated parameters, the actualvalues of type I error of the CS&Xmacr;chart does not match the specified value of it. Recently, Nedumaran and Pignatiello have presented an approach for constructing control limits of the &Xmacr;chart when those control limits are estimated using data from a small number of subgroups, based on the run length distribution. In this paper we construct a modified CS&Xmacr;chart for a small number of subgroups, based on the approach proposed by Nedumaran and Pignatiello. The performance of the proposed chart was compared with those of the usual CS&Xmacr;chart and the modified &Xmacr;chart constructed by Nedumaran and Pignatiello through the computer simulations.
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