Область применения

1.1 The purpose of this practice is to present concepts necessary to the understanding of the terms "precision" and "bias" as used in quantitative test methods. This practice also describes methods of expressing precision and bias and, in a final section, gives examples of how statements on precision and bias may be written for ASTM test methods. The term "accuracy", used in earlier editions of Practice E 177, embraces both precision and bias (see Section 20 and Note 4).

1.2 Informal descriptions of the concepts are introduced in the text as the concepts are developed, and appear in the following sections:

SectionTerminology3 Significance and Use4

GENERAL CONCEPTS

Test Method5 Measurement Terminology6Observation7 Test Determination8Test Result9

SOURCES OF VARIABILITY

Experimental Realization of a Test Method10Operator 11 Apparatus 12 Environment 13 Sample 14 Time 15

STATISTICAL CONCEPTS

Accepted Reference Value 16 Statistical Control 17 Precision 18 Bias 19 Accuracy 20 Variation of Precision and Bias with Material21 Variation of Precision and Bias with Sources of Variability22

COMBINATIONS OF SOURCES OF VARIABILITY

Repeatability and Laboratory Bias 23 Other Within-a-Single Laboratory Precisions24 Reproducibility and Bias of the Test Method25 Range of Materials 26

METHODS OF EXPRESSING PRECISION AND BIAS

Indexes of Precision 27Preferred Indexes of Precision for ASTM Test Methods 28 Preferred Statements of Bias for ASTM Test Methods 29 Elements of a Statement of Precision and Bias 30

STATEMENTS OF PRECISION AND BIAS

Examples of Statements of Precision and Bias31

<APPENDIXAlphabetical List of Descriptions of Terms from the Text X1

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.