5.1 This test method may be used for determining compliance with a specification for maximum cashmere coarse-hair content and is required to be used for determining compliance with Specification D2817.

5.1.1 In case of a dispute arising from differences in reported test results when using Test Method D2816 for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in the light of the known bias.

5.2 When the product being tested has a cashmere coarse-hair content that departs significantly either way from the specified amount, the sequential test procedure described herein will result in a substantial reduction in the number of observations required for a decision at the stated level of confidence. On the other hand, when the product being tested has a cashmere coarse-hair content that approaches the specified amount, the sequential procedure ensures that the necessary increased number of observations shall be made to secure a correct decision at the stated level of confidence.