Standard Practice for Interlaboratory Testing of a Textile Test Method That Produces Non-Normally Distributed Data

1.1 This practice covers design and analysis of interlaboratory testing of a test procedure in the case where the resulting test data are discrete variates or are continuous variates not normally distributed. This practice applies to all such interlaboratory tests used to validate a test procedure.

1.2 Analysis of interlaboratory test results permits validation that the process of using the test method is in statistical control and provides the information required to write statements on precision and bias as directed in Practice D2906. It also gives the information for determining the number of specimens per unit in the laboratory sample as required in Practice D2905.

1.3 Precision statements for non-normally distributed data can be written as a function of the level of the property of interest without an interlaboratory test if the underlying distribution is known and statistical control can be assumed.

1.4 If the underlying distribution is unknown, the precision of the test method can only be approximated. There are no generally accepted methods of making approximations of this sort.

1.5 If statistical control cannot be assumed, then a meaningful precision statement cannot be written and the test method should not be used.

1.6 This practice is intended for use with data from test methods that cannot be properly modeled by a normal distribution. See Practices D2904 and E691 for applications that can be modeled by a normal distribution.

1.7 This practice includes the following sections:

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