JIS-Z-9015-2-1999-R2005-ENG.pdf
JIS JIS Z 9015-2 :1999 JAPANESE IN DUSTRIAL STANDARD Translated and Published by Japanese Standards Association Sampling procedures for inspection by attributes- Part 2 :.Sampling plans indexed by limiting quality (LQ) for isolated lot inspection ICs 03.120.30 Descriptors : inspection by attributes, inspection by variables, counting, quality Reference number : JIS Z 9015-2 : 1999 (E) control, statistical quality control, sampling equipment, sampling tables 15 S Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/14/2007 02:19:48 MDTNo reproduction or networking permitted without license from IHS -,-,- STD-JIS Z 7015-2-ENGL 1797 H 4733b08 05b8477 570 9 2 9015-2 : 1999 Foreword This translation has been made based on the original Japanese Industrial Standard established by the Minister of International Trade and Industry through deliberations at the Japanese Industrial Standards Committee in accordance with the Industrial Standardization Law. To conform with the International Standard IS0 2859-3 : 1985 has been basically employed. JI$ Z 9015 : 1999 consists of the following parts under the title “Sampling procedures for inspection by attributes”. Part O : IntroductionOto the JIS Z 9015 attribute sampling system Part 1 : Sampling plans indexed by acceptable quality level (AQL) for Part 2 : Sampling plans indexed by limiting quality (LQ) for isolated Part 3 : Skip-lot sampling procedures lot-by-lot inspection lot inspection Date of Establishment: 1999-05-20 Date of Public Notice in Official Gazette: 1999-05-20 Investigated by: Japanese Industrial Standards Committee Divisional Council on Basic Items JIS Z 9015-2: 1999, First English edition published i n 2000-12 Translated and published by: Japanese Standards Association 4-1-24, Akasaka, Minato-ku, Tokyo, 107-8440 JAPAN In the event of any doubts arising as to the contents, the original JIS is to be the final authority. O JSA2000 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. Printed in Japan Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/14/2007 02:19:48 MDTNo reproduction or networking permitted without license from IHS -,-,- Contents Page Introduction . . 1 1.1 1.2 2 3 3.1 3.2 3.3 3.4 3.5 4 4.1 4.2 4.3 4.4 5 6 6.1 6.2 7 7.1 7.2 7.3 Scope and field of application . Scope Field of application . Definitions Choice of sampling plan . Specifying a sampling plan Choice of sampling procedure . Procedure A (use Attached Table A) Procedure B (use Attached Tables B) Choice of parameters for the sampling procedures . Rules for acceptance and non-acceptance . Sampling . Acceptance Nonconforming units . Non-acceptance and resubmission Double and multiple sampling plans . Examples illustrating how to use this part of JIS Z 9015 Example of procedure A . Example of procedure B . Compatibility with JIS Z 9015-1 General Procedure A (see Attached Table A) Procedure B (see Attached Tables B) Attached Tables 1 1 1 2 3 3 3 3 4 4 4 5 5 5 6 6 6 6 6 7 7 7 7 7 8 Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/14/2007 02:19:48 MDTNo reproduction or networking permitted without license from IHS -,-,- STD-JIS Z 7015-2-ENGL 1777 i733b08 05b81i77 3b3 JAPANESE INDUSTRIAL STANDARD JIS Z 9015-2 : 1999 Sampling procedures for inspection by attributes Part 2 : Sampling plans indexed by limiting quality (LQ) for isolated lot inspection Introduction This Japanese Industrial Standard has been prepared based on IS0 2859-2 Sampling procedures for inspection by attributes Part 2 : Sampling plans in- dexed by limiting quality (LQ) for isolated lot inspection issued in 1985 as the first edition without changing the technical contents. The “Informative references” underlined with dots in this Standard show the matters not specified in the original International Standard. JIS Z 9015-1 specifies the sampling inspection plans indexed by AQL. These sampling inspection plans are widely used in various cases. They are designed originally for lot-by-lot inspection and the switching rules are applied. This rule can give (by switching to tightened inspection and, moreover, interrupting the inspection) a pro- tection to the consumer on one hand, and give an incentive for quality improvement to the producers on the other hand. There are, however, many cases where the switching rules in JIS Z 9015-1 are unapplicable. A lot in an isolated state is a typical case. This Standard is designed to be complementary for JIS Z 9015-1 in a case like this. The sampling plans in this Standard are indexed by limiting quality (LQ) but not indexed directly by AQL. This is a big difference from the special procedure for lim- iting quality protection by JIS Z 9015-1. This Standard is made on the basis on the principle given below: a) b) C the new LQ plans can be easily integrated with the existing AQL plans in JIS Z 9015-1; the LQ indexing uses a preferred series of values that cannot be confused with the preferred series of AQL values; the five basic numbers associated with a single sampling plan, i.e. lot size, sample size, acceptance number, AQL (or producers risk quality) and LQ, appear in the same table, whenever possible. Informative reference : ISO/DIS 2859-1.2 : 1997 Sampling procedures for in- spection by attributes Part 1: Sampling plans indexed by acceptable quality level (AQL) for lot-by-lot inspec- tion is identical with JIS Z 9015-1. 1 Scope and field of application 1.1 Scope This part of JIS Z 9015 establishes LQ sampling plans and procedures for in- spection by attributes compatible with JIS Z 9015-1 that can be used when the switch- ing rules given in JIS Z 9015-1 are not applied, for example, when lots are of an isolated nature. Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/14/2007 02:19:48 MDTNo reproduction or networking permitted without license from IHS -,-,- STD-JIS Z 7015-2-ENGL 1777 4733b08 05bô500 705 W 2 Z 9015-2 : 1999 The plans in this part of JIS Z 9015 are indexed by a preferred series of limiting qualities (LQ) with a consumers risk usually below 10 %, but always below 13 %. This method of indexing permits the “ad-hoc” procedure mentioned in sub-clause 1 2 . 6 of JIS Z 9015-1 to be implemented as a standard procedure. Notes 1 The plans in JIS Z 9015-1 are indexed by a preferred series of AQL values and inspection levels. During the inspection of a continuing series of lots the application of switching rules helps to ensure that the process average in that series of lots is kept below the specified AQL. Limiting quality does not have the same direct relationship with the process average (see 3 . 5 . 1 ) . 2 JIS Z 9015-1 sub-clause 1 2 . 6 . 2 , states: “If the series of lots is not long enough to allow the switching rules to be applied, it may be de- sirable to limit the selection of sampling plans to those, associated with a designated AQL value, that give consumers risk quality not more than a specified limiting quality protection. Sampling plans for this purpose can be selected by choosing a consumers risk quality (CRQ) and a consumers risk to be associated with it. Attached Tables 6 and 7 give process levels for which the prob- abilities of lot acceptance under various sampling plans are 10 % and 5 %, respectively.” This part of JIS 2 9015 establishes preferred values for the LQ and allows the consumers risk to vary as indicated above. Informative reference : This Standard designed on the premise of nonconform- . -._-._- on the number of nonconforming products per 100 items - -.-.-_ . 1 . 2 Field of application situations often met in practice: a) Alternative procedures are provided in this part of JIS Z 9015 to cater for two Procedure A, to be used when the supplier and consumer both wish to regard the lot in isolation. The tables are based on random sampling from finite lots for both consumer and producer risks. This procedure shall be used unless there is a specific instruction to use procedure B. Procedure B, to be used when the supplier regards the lot as one of continu- ing series but the consumer considers the lot received in isolation. The tables are based on random sampling from a finite lot for consumers risk at the lim- iting quality, but random sampling from a process for the producers risk and the tabulated values of the operating characteristic (OC) curves. The plans used are a selection of the plans available in JIS Z 9015-1 so that a producer can maintain consistent procedures for customers whether or not they receive indi- vidual lots or a continuing series of lots. This procedure is suitable for inclu- sion in product standards or specifications that contain sampling clauses. a manufacturer will be concerned with all of his Droduction. but the individual consumer onlv with the Darticular lot received. Informative reference : The primary p q o s e of this Standhrd is to complement JIS _._-.-._ Z 9015-1 _._ (Sampling-procedures _-_._._._._. for _._._-_. inspection _._-_._ b2 attributes-Part 1 : Sampling plans indexed bj AQL for b) _._._._._-_._-.-_-.-._.-._-. _.-._ .-. . _._-_._._._. ._._._._-._-._-. ._._ .- ._._._._._._.-.- -_._._ _. Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/14/2007 02:19:48 MDTNo reproduction or networking permitted without license from IHS -,-,- STD*JIS Z 7015-2-ENGL 1777 m 4733b08 05b850l 841 3 Z 9015-2 1999 lot-by-lot inspection). This Standard can be used instead of JIS Z 9006 (Single sampling inspection plans with . screening by attributes) expected to be abolished with a view to improving the international conformity of JIS . . Informative reference : . sampling inspection standard system. Normative reference is not given in the original Inter- 1 is frequently referred to. In addition, important information on the use of this Standard is given in JIS . ?%ti.on.al .st?.?d?i.b,. I ! ! .PraCti_l .howexer2. .*s. z. 991 5.: . . Z 9015-0. . 2 Definitions The definitions given in JIS Z 9015-1 shall apply. Informative reference : . The definitions not given in JIS Z 9015-1 are given in JIS Z 8101-1 and JIS Z 8101-2. The provisions cited from IS0 3534-1 : 1993 Statistics-Vocabulary and sym- bols-Part . 1 : Probability and general statistical terms and . IS0 3534-2 : 1993 Statistics-Vocabulary and sym- bols-Part 2 : Statistical quality control are equivalent to the Corresponding provisions in the said standard. . 3 Choice of sampling plan 3 . 1 Specifying a sampling plan When reference is made to this part of JIS Z 9015 in a contract or specification, it is necessary to specify the procedure to be used (i.e. either A or B). In the ab- sence of any reference to either procedure, then procedure A shall be used. 3 . 2 Choice of sampling procedure Although procedure A is based on the hypergeometric distribution for sampling results, this distribution is well approximated by the binomial distribution for plans with non-zero acceptance numbers in procedure A. Hence the OC curves for these plans are well approximated by the tabulated performance of the same plans in procedure B. However, procedure A uses plans with acceptance number zero and with sample sizes based on the hypergeometric distribution of sampling results while procedure B excludes accept zero plans, replacing them with 100 % inspection. The choice between the procedures is dominated by the attitude towards accept zero plans. Procedure A uses accept zero plans linking the sample size and the lot size by the hypergeometric distribution until the proposed plan corresponds to the accept zero plan in JIS 2 9015-1 corresponding to that limiting quality. Thereafter the progression of sampling size and acceptance number with lot size is based on the inspection levels available in JIS Z 9015-1. The overall effect of procedure A resembles inspection level I for limiting quality less than 8 % and level II for limit- ing quality greater than 8 % with 8 % being intermediate between these levels. Procedure B provides greater flexibility in the choice of inspection levels. The tabulated OC curves are based on the probability of producing a nonconforming unit so they are approximately correct for small sampling fractions but as the sampling Copyright Japanese Standards Association Provided by IHS under license with JSALicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/14/2007 02:19:48 MDTNo reproduction or networking permitted without license from IHS -,-,- STDmJIS Z 70L5-2-ENGL 1777 V733bO8 05b8502 788 4 Z 9015-2 : 1999 fraction increases the curves (and tables) underestimate the probability of acceptance for good quality and underestimate the probability of rejection for poor quality. For sufficiently small lots, procedure B requires 100 % inspection. Both procedures treat the limiting quality (LQ) as the actual percent nonconforming units in the submitted lots and the probability of acceptance at this limiting quality can be found in Attached Table D1 for procedure A and Attached Tables B1 to B10 for procedure B. Procedure B is indicated as the appropriate procedure if the manu- facturer is concerned with a continuing series of lots; whether or not these go to the same consumer. Procedure A is indicated as the appropriate procedure when the lot is a single lot and shall be used if accept zero plans are required to be part of the sampling scheme. 3.3 Procedure A (use Attached Table A) A plan is identified by the lot size and the limiting quality (LQ). With the specified lot size and limiting quality as indexing values, the sampling size (n) and acceptance number (Ac) are given in Attached Table A. Although the primary index to these tables is the limiting quality (LQ), the pro- ducer/supplier needs guidance on the quality level required if lots are to have a high probability of acceptance. Information on the producers risk point is contained in Attached Table D1. Information on the probability of acceptance of relatively good lots by accept zero plans is given in Attached Table D2
