5.1 Limited accuracy in measuring the change in length produces errors in estimating values for shrinkage below 10 %. However, this test is being used for low level shrinkage fibers because the results give have been found to give an adequate indication of average shrinkage at the lower levels. The test is not adequate for determining variability in average shrinkage at low levels. If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, use the samples for such a comparative tests that are as homogeneous as possible, drawn from the same lot of material as the samples that resulted in disparate results during initial testing and randomly assigned in equal numbers to each laboratory. The test results from the laboratories involved should be compared using a statistical test for unpaired data, a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.

5.2 This test method for testing the shrinkage of fibers is not recommended for acceptance testing of commercial shipments of fibers because only a limited amount of data is available. See Section 14.

5.3 This test method may be used for acceptance testing of commercial shipments of fibers; but caution is advised since information on between laboratory precision is incomplete. Comparative tests as directed in 5.1 are advised.