ASTM D 2906 : 1997

1.1 This practice serves as a guide for using the information obtained as directed in Practice D2904 to prepare statements on precision and bias in ASTM methods prepared by Committee D-13. The manual on form and style for standards specifies that statements on precision and bias be included in test methods. Committee D-13 recommends at least a statement about single-operator precision in test methods. Whenever applicable, a statement on precision based on values from a statistical analysis of interlaboratory data is expected in tentative methods proposed for adoption as standard.

1.2 The preparation of statements on precision and bias requires a general knowledge of statistical principles including the use of components of variance estimated from an analysis of variance. Instructions covering such calculations are available in Practice D2904 or in any standard text (1, 2, 3, 4, and 5).

1.3 The instructions in this practice are specifically applicable to test methods in which test results are based ( ) on the measurement of variables, ( ) on the number of successes or failures in the specified number of observations, ( ) on the number of defects or incidents counted in a specified interval or in a specified amount of material, and ( ) on the presence or absence of an attribute in a test result (a go, no-go test). Instructions are also included for methods of test for which precision has not yet been estimated or for which precision and accuracy have been reported in another method of test. For observations based on the measurement of variables, the instructions of this practice specifically apply to test results that are the arithmetic average of individual observations. With qualified assistance, the same general principles can be applied to test results that are based on other functions of the data such as standard deviations.

1.4 This standard includes the following sections:

Section No. Attributes, Statements Based on 15 Binomial Distributions, Calculations for 9 Binomial Distributions, Statements Based on 13 Categories of Data 7 Computer Preparation of Statements Based on Normal or Trans- 12 formed Data Normal Distributions and Transformed Data, Calculations for 8 Normal Distributions and Transformed Data, Statements Based on 11 Poisson Distributions, Calculations for 10 Poisson Distributions, Statements Based on 14 Precision and Bias Based on Other Methods 16 Precision Not Established, Statements When 17 Ratings, Statements Based on Special Cases of 18 Sources of Data 6 Statistical Data in Two Sections of Methods 5 Significance and Use 4