1 Introduction common method of assessing the quality of the output of a proces is Statistical Proces curb (SPC).

1 Introduction

common method of assessing the quality of the output of a proces is Statistical Proces curb (SPC). A sample consisting of the last n units produc is taken at intervals of h hours of production. Each sampled unit is inspected, and these data are used to calculate a sample statistic(s) that is used to decide whether an assignable cause is not absent in the process ("out of control") or not ("in control") Conclusions about the state of the proces are control to the usual sampling errors.

In this paper, we examine the case where the sampled units are