Jun 3, 2018 - ANSI/ASQ Z1.9-2003 (R2013) Sampling Procedures and Tables for. ANSI ASQ Z1.9-2008 - Download as PDF File (.pdf), Text File (.txt). Ansi/asq z1.4-2003 american society for quality 600 north plankinton avenue milwaukee, wisconsin 53203 american national standard sampling procedures and tables for inspection.
Purchase as a set with Z1.9-2008 and save! Sampling Procedures and Tables for Inspection by Attributes is an acceptance sampling system to be used with switching rules on a continuing stream of lots for AQL specified.
It provides tightened, normal, and reduced plans to be applied for attributes inspection for percent nonconforming or nonconformities per 100 units.
INTRODUCTION This standard was prepared to meet a need for the use of standard sampling plans for inspection by variables in procurement, supply and storage, and maintenance inspection operations. The variables sampling plans apply to a single quality characteristic which can be measured on a continuous scale, and for which quality is expressed in terms of percent nonconforming. The theory underlying the development of the variables sampling plans, including the operating characteristic curves, assumes that measurements of the quality characteristics are independent, identically normally distributed random variables.
It is important to note that variables sampling plans are not to be used indiscriminately, simply because it is possible to obtain variables measurement data. The users are advised to consult their technical agency to determine the feasibility of application in considering applications where the normality or independence assumptions may be questioned. In comparison with attributes sampling plans, variables sampling plans have the advantage of usually resulting in considerable savings in sample size for comparable assurance as to the correctness of decisions in judging a single quality characteristic, or for the same sample size, greater assurance is obtained using variables plans. Attributes sampling plans have the advantage of greater simplicity, of being applicable to either single or multiple quality characteristics, and of requiring no knowledge about the distribution of the continuous measurements of any of the quality characteristics. This standard is divided into four sections.
Section A describes general procedures of the sampling plans. Sections B and C describe specific procedures and applications of the sampling plans when variability is unknown.
In Section B the standard deviation is used as the basis for an estimate of the unknown variability, and in Section C the average range of the sample is used. Section D describes the plans when variability is known. Each of Sections B, C, and D is divided into two parts: (I) Sampling Plans for the Single Specification Limit Case, and (II) Sampling Plans for the Double Specification Limit Case. For the single specification limit case, the acceptability criterion is given in two forms: Form 1 and Form 2. Either of the forms may be used, since they are identical as to sample size and decision for lot acceptability or rejectability. In deciding whether to use Form 1 or Form 2, the following points should be borne in mind.
Form 1 provides the lot acceptability criterion without estimating lot percent nonconforming. The Form 2 lot acceptability criterion requires estimates of lot percent nonconforming. Operating characteristic curves in Table A-3 are for the Normal Inspection sampling plans and show the relationship between quality and percent of lots expected to be accepted for the quality characteristic inspected. As stated, these operating characteristic curves are based on the assumption that measurements are selected at random from a normal distribution. The corresponding sampling plans in Sections B, C, and D were matched as closely as possible under a system of fixed sample size with respect to their operating characteristic curves. Operating characteristic curves in Table A-3 have been computed for the sampling plans based on the standard deviation estimate of unknown variability.
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