5.1 This test method is considered satisfactory for acceptance testing of commercial shipments since current estimates of between-laboratory precision are acceptable, and this test method is used extensively 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. Test specimens then should be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using the appropriate statistical analysis and an acceptable probability level chosen by the two parties before 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 with consideration to the known bias.

5.2 Thickness is one of the basic physical properties of textile materials. In certain industrial applications, the thickness may require rigid control within specified limits. Bulk and warmth properties of textile materials are often estimated from their thickness values, and thickness is also useful in measuring some performance characteristics, such as before and after abrasion and shrinkage.

5.3 The thickness value of most textile materials will vary considerably depending on the pressure applied to the specimen at the time the thickness measurement is taken. In all cases, the apparent thickness varies inversely with the pressure applied. For this reason, it is essential that the pressure be specified when discussing or listing any thickness value.

5.4 When using this test method for measuring the thickness of textile materials, the primary method for the specific material such as listed in the Referenced Document section shall take precedence over the directions described in this test method, unless specifically provided for in that test method. This test method is used in its entirety when no test method for measuring thickness is available for the specific material to be tested or unless otherwise specified in a material specification or contract order.