AATCC 127-2017 Water Resistance: Hydrostatic Pressure Test.
10. Precision and Bias
10.1 Precision. The test results are tester dependent. Precision statements for each tester are given in 10.2 and 10.3.
10.2 Suter Hydrostatic Pressure Tester (Option 1).
10.2.1 In 1993, a limited interlaboratory study was completed, which in- cluded six laboratories, two operators in each, running determinations on three specimens of two fabrics. No prior as- sessment was made of the relative level of the participating laboratories on per- formance of the test method.
10.2.2 The two fabrics were at different levels (Fabric 1 approximately 810 mm and Fabric 2 approximately 340 mm), and residual variances of the two fabrics were found to be different. Ac- cordingly, precision is reported separately for each fabric.
10.2.3 Users of the method are advised of the limited nature of this study and advised to apply these findings with due caution. 10.2.4 Analysis of the data sets for each fabric yielded components of variance and critical differences as displayed in Tables I, II and III. Differences between two averages of (N) determinations, for the appropriate precision parameter, should reach or exceed the table value to be statistically significant at the 95% confidence level. 10.3 Hydrostatic Head Tester (Option 2). 10.3.1 In a singlelaboratory study, six different laboratory technicians ran determi nations on three specimens of five fabrics.
10.3.2 The five fabrics were at differ- ent levels of approximately: A=103, B=33, C=37, D=12, and E=77. Data ob- tained in this study is recorded in millibars (SI standard). The residual variance of the five fabrics were found to be dif- ferent, therefore, precision is reported separately for each. 10.3.3 Analysis of the data sets for each fabric yielded critical differences as shown in Tables IV, V, VI, VII and VIII. Differences between two averages of (N) determinations, for the appropriate preci- sion parameter, should reach or exceed the table value to be statistically signifi- cant at the 95% confidence level.
10.3.4 Between laboratory precision has not been established for this option. Until such precision information is available, users of this method should use standard statistical techniques in making any comparison of test results for be tween laboratory averages.
10.4 Bias.
10.4.1 Water resistance of fabrics can only be defined in terms of a test method. There is no independent, referee method for determining the true value. This test method has no known bias.
11. Notes
11.1 For potential equipment information pertaining to this test method, please visit the online AATCC Buyer’s Guide at www. aatcc.org/bg. AATCC provides the possibility of listing equipment and materials sold by its Corporate members, but AATCC does not qualify, or in any way approve, endorse or certify that any of the listed equipment or materials meets the requirements in its test methods.
11.2 Hydrostatic Pressure Tester (Suter).
11.2.1 The apparatus consists essentially of an inverted conical well equipped with a coax- ial ring clamp to fasten the cloth specimen under the well bottom. The apparatus introduces water from above the specimen over an area 114 mm in diameter and at a rate of 10.0 ± 0.5 mm of hydrostatic head per second. A mirror is affixed below the specimen to enable the operator to ascertain penetration of the specimen by drops of water. A valve is provided for venting the air in the well.
11.2.2 Hydrostatic testing apparatus of the type described is no longer available for sale.
11.3 Hydrostatic Head Tester.AATCC 127 pdf download.