ISO 13909-7:2016 無煙炭とコークス—機械的サンプリング—パート7：サンプリング、サンプル準備、およびテストの精度を決定する方法 | ページ 2

Foreword

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The committee responsible for this document is ISO/TC 27, Solid mineral fuels, Subcommittee SC 4, Sampling.

This second edition cancels and replaces the first edition (ISO 13909-7:2001), which has been technically revised.

ISO 13909 consists of the following parts, under the general title Hard coal and coke — Mechanical sampling:

• Part 1: General introduction
• Part 2: Coal — Sampling from moving streams
• Part 3: Coal — Sampling from stationary lots
• Part 4: Coal — Preparation of test samples
• Part 5: Coke — Sampling from moving streams
• Part 6: Coke — Preparation of test samples
• Part 7: Methods for determining the precision of sampling, sample preparation and testing
• Part 8: Methods of testing for bias

Introduction

Two different situations are considered when a measure of precision is required. In the first, an estimate is made of the precision that can be expected from an existing sampling scheme and, if this is different from that desired, adjustments are made to correct it. In the second, the precision that is achieved on a particular lot is estimated from the experimental results actually obtained using a specifically designed sampling scheme.

The formulae developed in this part of ISO 13909 are based on the assumption that the quality of the fuel varies in a random manner throughout the mass being sampled and that the observations will follow a normal distribution. Neither of these assumptions is strictly correct. Although the assumption that observations will follow a normal distribution is not strictly correct for some fuel parameters, this deviation from assumed conditions will not materially affect the validity of the formulae developed for precision checking since the statistics used are not very sensitive to non-normality. Strictly speaking, however, confidence limits will not always be symmetrically distributed about the mean. For most practical uses of precision, however, the errors are not significant.

1 Scope

In this part of ISO 13909, formulae are developed which link the variables that contribute to overall sampling precision. Methods are described for estimating overall precision and for deriving values for primary increment variance which can be used to modify the sampling scheme to change the precision. Methods for checking the variance of sample preparation and testing are also described.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13909-1 apply.

Bibliography