Significance and Use
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 D 2817
In case of a dispute arising from differences in reported test results when using Test Method D 2816 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.
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.
1.1 This test method covers a sequential procedure for determining whether or not the cashmere coarse-hair content of a sample exceeds a specified value.
Note 1—For the maximum allowable cashmere coarse-hair content in cashmere, refer to Specification D 2817
Note 2—For the quantitative analysis of cashmere hair and blends of cashmere hair and other fibers, refer to Test Methods D 629
1.2 This test method is applicable only to cashmere hair in the form of roving, yarn, or fabric, and to the cashmere hair content of blends with other fibers, where the expected cashmere coarse-hair content is not more than five mass percent (see Footnote C of Table 1). For greater expected mass percentages of cashmere coarse-hair, see Test Methods D 629
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
TABLE 1 Sequential Accept-Reject Numbers for Selected SpecificationsA
|Number of Fi-|
|Specification, Length %B|
A These accept-reject numbers are based on the following conditions:
(1) The probability of accepting a lot that exceeds the specifications by 10 % or more of the specification percent is 0.05.
(2) The probability of rejecting a lot that is 10 % or more of the specification percent below the specification is also 0.05.
B Extensive interlaboratory tests have shown that, for the concentration of cashmere coarse-hair covered in Table 1, the relationship between “Specification, Length Percent” and mass percent of cashmere coarse-hair is approximately linear, as shown in (Eq 1):
|=||mass percent of cashmere coarse-hair, and|
|=||specified maximum coarse-hair content in length percent (0.2 ≤ S ≤ 1.0).|
The data from these studies are on file with the Secretary of Subcommittee D13.13, Committee D13 of ASTM.
C Blanks correspond to a theoretical number less than zero. No decision to accept can be made until a number of fibers corresponding to the first nonblank entry has been classified.