ANSI ASQ Q3-1988 Sampling Procedures and Tables for Inspection of Isolated Lots by Attributes (T36E).pdf

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1、ANSVASQC Standard Q3-1988 AMERICAN NATIONAL STANDARD AMERICAN SOCIETY FOR QUALITY 61 1 East Wisconsin Avenue Milwaukee, Wisconsin 53202 ANSVASQC Standard (23-1988 AMERICAN NATIONAL STANDARD Sponsors: American Society for Quality and U.S. TAG to IS0 TC69 on Statistical Methods (U.S. Technical Advisor

2、y Group for International Organization for Standardization Technical Committee 69 on Applications of statistical methods) ABSTRACT Sampling Procedures and Tables for Inspection of Isolated Lots by Attributes is an acceptance sampling system to be used when one or more lots that are isolated or separ

3、ated from a continuous stream of lots are sub- mitted for acceptance. For this purpose the quality levels referenced in this standard are indexed by Limiting Quality (LQ) . The LQ represents the quality of a lot the consumer does not wish to accept. The probability of acceptance of a lot which has a

4、 quality equal to or worse than the LQ is purposely low. Plans provide for the judgment of lots based on the percent nonconforming or the nonconformities per hundred items. The procedures of this standard differ from those of ANSIIASQC 21.4 Sampling Procedures and Tables for Inspection by Attributes

5、 which is appropriate for a continuous stream of lots with an Acceptable Quality Level (AQL) specified. AMERICAN NATIONAL STANDARD: An American National Standard implies a consensus of those substantially concerned with its scope and provisions. An American National Standard is intended as a guide t

6、o aid the manufacturer, the consumer, and the general public. The existence of an American National Standard does not in any respect preclude anyone, whether he has approved the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to

7、the standard. American National Standards are subject to periodic review, and users are cautioned to obtain the latest editions. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute require that action be

8、 taken to reaffirm, revise, or withdraw this standard no later than five years from the date of approval. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Approved May 10, 1988 American Nationa

9、l Standards Institute, Inc. Copyright 0 1988 by the AMERICAN SOCIETY FOR QUALITY No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Published by: American Societv for Qualitv Quality Press

10、61 1 East Wisconsin Avenue PO. Box 3005 Milwaukee. Wisconsin 53201-3005 Printed in the United States of America. 11 (This foreword is not a part of American National Standard Sampling Procedures and Tables for hspection of Isolated Lots by Attributes.) This standard indexes tables by Limiting Qualit

11、y (LQ) values, a quality level which a consumer wishes not to accept. The indexing by LQ values identified by the 0.5,0.8, 1.25,2.0, 3.15, and 5.0 series, which is different from the Acceptable Quality Level (AQL) values used in ANSUASQC 21.4, helps to distinguish between LQ- and AQL-oriented specif

12、ications. The AQL represents a quality level for which the probability of lot acceptance is high, whereas LQ represents a quality level for which the probability of lot acceptance is low. Many of the sampling plans and lot sizes are consistent with ANSI/ASQC 21.4 This standard complements ANSUASQC 2

13、1.4-1981, which applies primarily to a continuing stream of lots, but which, by means of Tables VIA and VIB, provides for inspection of isolated lots indexed by LQ values. Tables VIA and VIB of ANSI/ASQC 21.4 have been difficult to apply due to the indexing method using the AQL and due to insufficie

14、nt instructions on how to convert LQ values to AQL values. The procedures and tables of this standard are similar to those presented in IS0 285912 (formerly IS0 7362) and are based on the work of the International Organization for Standardization Technical Committee 69, Applications of statistical m

15、ethods, and the work presented in a paper entitled, “Single Sampling Plans Indexed by LQLs that Are Compatible with the Structure of MIL-STD lOSD,” by Acheson J. Duncan, August B. Mundel, A. Blanton Godfrey, and Valerie A. Partridge, in the Journal of Quality Technology 12, No. 1 (January 1980). Com

16、mittee members serving as writers and editors of this standard were: August B. Mundel, Chairman Burton S. Liebesman Oswald Willner Sherman Babcock iii ANSIJASQC Standard 43-1988 Sampling Procedures and Tables for Inspection of Isolated Lots by Attributes Table of Contents O . INTRODUCTION . 1 1 . PU

17、RPOSE 1 2.SCOPE 1 2.1 Application 1 2.2Inspection . 1 2.3 Inspection by Attributes 2 2.4UnitofProduct . 2 3 . DEFINITIONS AND TERMINOLOGY . 2 3.1 Defect 2 3.2 Nonconformity . 2 3.3 Acceptable Quality Level (AQL) 2 3.4 Limiting Quality (LQ) . 2 3.5 IsolatedLot . 2 3.6 Mixed Lot 2 4 . EXPRESSION OF CO

18、NFORMANCE . 2 4.1 Percent Nonconforming and Nonconformities per Hundred Units 2 4.3 Nonconformities per Hundred Units . 3 4.2PercentNonconforming 3 5 . LIMITING QUALITY (LQ). USE OF PLANS . 3 5.1 Use 3 5.2 Note on the Meaning of LQ 3 5.3 Limitation . 3 5.4 Specifying LQs 3 5.5 Nominal Limiting Quali

19、ty Levels 3 6 . SUBMISSION OF PRODUCT . 3 6.1 Lot or Batch . 3 6.2 Formation of Lots or Batches . 4 6.2.1 Formation of Type B Lots or Batches . 4 6.2.2 Formation of Type A Lots or Batches . 4 6.3 Lot or Batch Size . 4 6.4 Presentation of Lots or Batches . 4 7 . ACCEPTANCE AND NONACCEPTANCE 4 7.1 Acc

20、eptability of Lots or Batches . 4 7.2 Nonconforming Units . 4 7.3 Special Reservation for Designated Nonconformities 4 7.4 Resubmitted Lots or Batches 5 V ANSIIASQC Standard Q3-1988 8 . DRAWING OF SAMPLES . 5 8.1 Sample 5 8.2 Sampling 5 8.3 Time ofsampling . 5 8.4 Double or Multiple Sampling . 5 9 .

21、 NORMALINSPECTION 5 9.1 Normal Inspection 5 10 . SAMPLING PLANS 5 10.1 Sampling Plan 5 10.2Inspection Level 5 10.3Code Letters . 6 10.4 Obtaining the Sampling Plan 6 10.5 qpes of Sampling Plans . 6 11 . DETERMINATION OF ACCEPTABILITY . 6 11.1 Percent Nonconforming Inspection . 6 11.1.1 Single Sampli

22、ng Plan . 6 11.1.2 Double Sampling Plan 6 11.1.3 Multiple Sampling Plan . 6 11.3 Zero Acceptance Numbers 7 11.5 Nonstandard LQs . 7 11.2 Nonconformities per Hundred Units Inspection . 6 11.4PreferredLQs 7 12 . SUPPLEMENTARY INFORMATION 7 12.1 Operating Characteristic Curves . 7 12.2Process Average 7

23、 13 . TABLES (DESCRIPTION. APPLICATION. USE) . 8 13.1Table Al 8 13.2TableA2 8 l3.3TablesBl-B10 8 13.4TableCl 8 13.5Tables C2 andC3 . 8 13.6TableC4 9 TABLES Al . Single Sampling Plans Indexed by Nominal Limiting Quality (LQ) for Isolated Lots from Mixed and Uncontrolled Process Sources . 10 A2 . Summ

24、ary of Properties of LQ Plans Listed in Table Al . 11 B1-B10 . Single Sampling Plans Indexed by LQ for Isolated Lots from a Controlled Process . 12.21 B1 . Single Sampling Plans for Nominal Limiting Quality 0.5% 12 B3 . Single Sampling Plans for Nominal Limiting Quality 1.25%. 14 B4 . Single Samplin

25、g Plans for Nominal Limiting Quality 2.0%. . W B2 . Single Sampling Plans for Nominal Limiting Quality 0.8%. 13 B5 . Single Sampling Plans for Nominal Limiting Quality 3.15%. . 16 B6 . Single Sampling Plans for Nominal Limiting Quality 5.0%. 17 vi ANSIIASQC Standard Q3-1988 B7 . Single Sampling Plan

26、s for Nominal Limiting Quality 8.0%. 18 B8 . Single Sampling Plans for Nominal Limiting Quality 12.5%. 19 B9 . Single Sampling Plans for Nominal Limiting Quality 20.0%. 20 BIO . Single Sampling Plans for Nominal Limiting Quality 32.0%. 21 Cl . Relation Between Nominal Limiting Quality (LQ) and LQ,.

27、LQ, . 22 C2 . Equivalent Sample Sizes for Single. Double. and Multiple Plans . 22 C3 . Equivalent Acceptance Numbers for Single. Double. and Multiple Plans . 23 C4 . Probability of Zero Nonconforming Items in a Lot . 23 vii ANSIIASQC Standard Q3-1988 Sampling Procedures and Tables for Inspection of

28、Isolated Lots by Attributes O. INTRODUCTION When purchasing or accepting an isolated lot, the customer may specify a Limiting Quality (LQ). An LQ sampling plan specifies a quality the purchaser wishes to accept infrequently. Therefore, the risk of accepting a lot containing so many nonconforming uni

29、ts that the LQ obtains must be small. There are certain precautions that a vendee must exercise in specifying an LQ, and there are likewise precautions that a vendor must exercise when accept- ing an order which specifies an LQ. It must be recognized by both vendor and vendee that a lot containing a

30、 fraction nonconforming equal to or worse than the LQ has a very low probability of being accepted. To provide a satisfactory relation- ship between the producer and the purchaser, the lot shipped must have a very high probability of ac- ceptance, (P,). The lot must therefore be the result of a proc

31、ess in which the fraction nonconforming is small when compared to the specified LQ. For this reason, a summary of sampling plan properties for the sampling plans of Table Al are given in Table A2. Table A2 contains the quality levels associated with P, = 95% for each LQ indexed sampling plan. A vend

32、or who is producing a series of lots, one or a few of which are to be sent to a customer who will consider them as isolated lots, must also know the process levels that have a high probability of accept- ance. Tables B are provided to present the AQL values (from ANSI/ASQC 21.4) which have a high pr

33、oba- bility of acceptance as isolated lots shipped from a series of lots at specified LQ values. 1. PURPOSE This publication establishes sampling plans and procedures for inspection of isolated lots by attributes. The sampling plans contained herein are indexed by the same lot sizes used in ANSVASQC

34、 21.4 Sampling Procedures and Tables for Inspection by Attributes. When specified by the responsible authority: this publication shall be referenced in the specification, contract, inspection instructions, or other documents, and the provisions set forth herein shall govern. The “responsible authori

35、ty” shall be designated in one of the above documents, as agreed to by the purchaser and seller or producer and user. 2. SCOPE 2.1 Application Sampling plans designated in this publication are applicable, but not limited, to inspection of the following: a. end items b. components and raw materials c

36、. services d. materials in process e, supplies in storage f. data or records g. administrative procedures These plans are intended primarily for the inspection of isolated lots or batches. Type A lots are lots which both consumer and producer consider to be isolated. (Type A lots include mixed lots

37、and lots with different date codes.) When Type A lots are to be sampled, Table Al shall be used. Type B lots are lots which the producer considers or knows to be a lot or part of a lot from a continuous production series, but which the consumer receives as an isolated lot with no preceding or follow

38、-on lots. When Type B lots are to be sampled, Tables BI-BIO shall be used, provided that acceptable evidence of process control is pre- sented. When no such evidence is presented the ven- dee is advised to use the sampling plans of Table Al. 2.2 Inspection Inspection is the process of measuring, exa

39、mining, testing, or otherwise comparing the unit of product with the requirements, The responsible authority may be the contracting officer or his representative, or the purchasers man- agement as identified in a contract, agreement, or specification. 1 STD-ASQ Q3-ENGL L988 075750b D002b47 qb0 D ANS

40、IIASQC Standard Q3-1988 2.3 Inspection by Attributes Inspection by attributes is inspection whereby either the unit of product is classified simply as conforming or nonconfbrming, or the number of nonconformities in the unit of product is counted, with respect to a given requirement or set of requir

41、ements. 2.4 Unit of Product The unit of product is the unit inspected in order to determine its classification as conforming or noncon- forming, or to count the number of nonconformities. It may be a single article, a pair, a set, a length, an area, an operation, a volume, a component of an end prod

42、uct, or the end product itself. The unit of product may or may not be the same as the unit of purchase, supply, production, or shipment. 3. DEFINITIONS AND TERMINOLOGY The definitions and terminology employed in this standard are in accord with ANSIIASQC A2 Terms, Symbols, and Definitions for Accept

43、ance Sampling. The following definitions are particularly important in applying the standard. 3.1 Defect A departure of a quality characteristic from its in- tended level or state that occurs with a severity suf- ficient to cause an associated product or service not to satisfy intended normal, or fo

44、reseeable, usage requirements. 3.2 Nonconformity A departure of a quality characteristic from its in- tended level or state that occurs with severity suffi- cient to cause an associated product or service not to meet a specification requirement. These acceptance sampling plans for attributes are giv

45、en in terms of the percent or proportion of product in a lot or batch that depart from some requirement. The general terminology used within the document will be given in terms of percent of nonconforming units or number of nonconformities, since these terms are likely to constitute the most widely

46、used criteria for acceptance sampling. The standard is consistent with ANSIIASQC 21.4 in terminology, and some definitions used in this stan- 2 dard are also defined in ANSIJASQC A2? 3.3 Acceptable Quality Level (AQL) When a continuous series of lots is considered, the quality level which for the pu

47、rpose of sampling inspection is the limit of a satisfactory process average. 3.4 Limiting Quality (W) When a lot is considered in isolation, a quality level which, for the purpose of sampling inspection, has a low probability of acceptance. 3.5 Isolated Lot A lot separated from the sequence of lots

48、in which it was produced or collected and not forming part of a current sequence of inspection lots. 3.6 Mixed Lot A lot collected from a number of sources or from different production dates, machines, or processes. When mixed lots are sampled Table Al shall be used. When the lot to be sampled is on

49、e which the producer considers or knows to be a lot or part of a lot from a continuous production series, but which the consumer receives as an isolated lot with no preceding or follow-on lots, Tables BI-BIO shall be used, provided that acceptable evidence of process control is presented. When no such evidence is presented, the vendee is advised to use the sampling plans of Table Al. 4. EXPRESSION OF CONFORMANCE 4.1 Percent Nonconforming and Nonconfor- The extent of nonconformance of product shall be expressed either in terms of percent nonconforming or in terms of nonconformities per