This test method is considered satisfactory for acceptance testing of commercial shipments because current estimates of between-laboratory precision are acceptable and the method is used extensively in the trade for acceptance testing.

5.1.1 If there are differences or practical signficance 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, the test samples to be used are as homogeneous as possible, are drawn from the material from which the disparate test results are obtained, and are assigned randomly in equal numbers to each laboratory for testing. Other materials with established test values may be used for this purpose. The test results from the two laboratories should be compared using a statistical test for unpaired data, at 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 must be adjusted in consideration of the known bias.

Elapsed time between spinning and testing has a marked effect on the results of the draw tension test, especially during the first 24 h. Therefore, if tested within 24 h of spinning, specimens should be compared only if tested after the same elapsed time. No specimen should be tested within 4 h of spinning because the aging process is at its most rapid rate during this period, and the differences in rate due to fiber structure are most pronounced.

The extension force of manufactured filament yarns is related to the alignment of the molecules in the yarn filaments, which influences the yarn processing behavior. Knowledge of this property of partially oriented yarn is useful to determine processing conditions.