5.1 The testing procedure in this test method for the determination of staple length is considered satisfactory for acceptance testing of commercial shipments of grease wool since the test method has been used in the trade for acceptance testing.

5.1.1 In case of a dispute arising from differences in reported test results when using this test method 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 The test method is used for the determination of the average unstretched staple length and the staple length distribution of a lot of wool in order to assign length classes when determining the conformance of lots and shipments to length specifications.

5.3 In this test method, the size of a lot covered by the test procedure is limited to not more than 200 packages per test. Any shipment exceeding the above limits is divided into lots within the prescribed limits.

5.4 The nature of the sampling procedure is such that grease wool staples as originally drawn from the wool of the lot require only a slight amount of preparation before measurement. The bulk and laboratory samples are synonymous in this test method.

5.5 Compression of wool in the bale makes it difficult to penetrate the interior of the bale with the sampling tool. However, staples can be drawn from the surface of the bale with the sampling tool or by hand.

5.6 Practice D4271 contains information on how to write a section on sampling in test methods.

Note 2-An extensive discussion of grease wool staple sampling can be found in the literature.⁵