ISO 22514-2:2017 プロセス管理における統計的手法—機能とパフォーマンス—パート2：時間依存プロセスモデルのプロセス機能とパフォーマンス | ページ 2

3.1 記号

C p	工程能力指数
C パック	最小工程能力指数
	工程能力指数が低い
	上流工程能力指数
c _	サブグループサイズn に基づく定数
Δ	プロセスの分散
L	X MidとX の差 製品特性の分布の0.135%
U	製品特性の分布のX 99.865%とX 中央の差
d _	サブグループサイズn に基づく定数
k	同じサイズのサブグループの数n
μ	プロセスの平均的な位置
L	下側規格限界
M l, d	位置法ラベルl と分散法ラベルd を使用した計算方法
N	サンプルサイズ
L	下限不適合
p t	合計不適合率
U	上部部分が不適合
P p	プロセスパフォーマンス指数
P パック	最小プロセスパフォーマンス指数
	プロセスパフォーマンス指数が低い
	上流工程性能指数
i	i 番目のサブグループの範囲
s	標準偏差、実現値
σ	標準偏差、母集団
S	標準偏差、標本統計量
i	i 番目のサブグループの観察されたサンプル標準偏差
S t	標準偏差、下付き文字「t」は合計標準偏差を示します
U	規格上限値
X 0.135%	0.135% 分布分位数
X 99.865%	99.865% の分布分位数
X 50%	50% 分布分位数
X ミッド	分布の中間点

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives ).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents ).

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html

The committee responsible for this document is ISO/TC 69, Applications of statistical methods, Subcommittee SC 4, Applications of statistical methods in process management.

This second edition of ISO 22514-2 cancels and replaces the corrected version of the first edition (ISO 22514-2:2013), of which it constitutes a minor revision.

The changes compared to the previous edition are as follows:

• Table 2, row “Location”, column “C”, the letter “s” has been replaced by “s/r”;
• Table 2, row “Location”, column “D”, the capital letter “S” has been replaced by “s/r”;
• Table 3, row “Location method label”, rows “3” and “4” – in Formulae (13) and (14) the usage of indices has been improved and it is more precise now;
• editorial adjustments have been made to comply with the latest edition of the ISO/IEC Directives, Part 2, 2016.

A list of all parts in the ISO 22514- series, published under the general title Statistical methods in process management — Capability and performance, can be found on the ISO website.

Introduction

Many standards have been created concerning the quality capability/performance of processes by international, regional and national standardization bodies and also by industry. All of them assume that the process is in a state of statistical control, with stationary, normally distributed processes. However, a comprehensive analysis of production processes shows that, over time, it is very rare for processes to remain in such a state.

In recognition of this fact, this document provides a framework for estimating the quality capability/performance of industrial processes for an array of standard circumstances. These circumstances are categorized based on the stability of the mean and variance, as to whether they are constant, changing systematically, or changing randomly. As such, the quality capability/performance can be assessed for very differently shaped distributions with respect to time.

In other parts of ISO 22514 more detailed information about calculations of indices can be found. It should be noted that where the capability indices given in this document are computed they only form point estimates of their true values. It is therefore recommended that wherever possible the indices’ confidence intervals are computed and reported.

1 Scope

This document describes a procedure for the determination of statistics for estimating the quality capability or performance of product and process characteristics. The process results of these quality characteristics are categorized into eight possible distribution types. Calculation formulae for the statistical measures are placed with every distribution.

The statistical methods described in this document only relate to continuous quality characteristics. They are applicable to processes in any industrial or economical sector.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms definitions, symbols and abbreviated terms

For the purposes of this document, the terms and definitions given in ISO 3534-2 and ISO 22514-1, and

the symbols and abbreviated terms given below, apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

3.1 Symbols

Cp	process capability index
Cpk	minimum process capability index
	lower process capability index
	upper process capability index
c4	constant based on subgroup size n
Δ	dispersion of the process
ΔL	difference between Xmid and X0,135 % of the distribution of the product characteristic
ΔU	difference between X99,865 % and Xmid of the distribution of the product characteristic
d2	constant based on subgroup size n
k	number of subgroups of the same size n
μ	average location of the process
L	lower specification limit
M l,d	calculation methods with location method label l and dispersion method label d
N	sample size
pL	lower fraction nonconforming
pt	total fraction nonconforming
pU	upper fraction nonconforming
Pp	process performance index
Ppk	minimum process performance index
	lower process performance index
	upper process performance index
Ri	range of the ith subgroup
s	standard deviation, realized value
σ	standard deviation, population
S	standard deviation, sample statistic
Si	observed sample standard deviation of the ith subgroup
St	standard deviation, with the subscript “t” indicating total standard deviation
U	upper specification limit
X0,135 %	0,135 % distribution quantile
X99,865 %	99,865 % distribution quantile
X50 %	50 % distribution quantile
Xmid	distribution midpoint

3.2 Abbreviated terms

Bibliography