Acceptance Sampling for Percent Defective by Variables and by Attributes

Various methods for adjusting variables and attributes sampling plans so that they possess nearly identical OC curves are reviewed and extended. It is demonstrated that the OC curve for s-method plans can be adequately derived from a normal approximation and that the more complicated use of the noncentral t-distribution can be avoided. The relative efficiencies of the different types of single sampling plans are shown to be practically functions of the indifference quality alone. The relation between these efficiencies and the choice of the specification limit are discussed in detail.