5.1 This test method is intended either as an index test or as a performance test used to determine and compare the flow rate per unit width of one or several candidate geosynthetics under specific conditions.

5.2 This test method may be used as an index test for acceptance testing of commercial shipments of geosynthetics but caution is advised since information on between-laboratory precision of this test method is incomplete. Comparative tests as directed in 5.2.1 may be advisable.

5.2.1 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 first confirm that the tests were conducted using comparable test parameters including specimen conditioning, normal stress, seating period, hydraulic gradient, test water temperature, etc., then 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 homogenous as possible and that are formed from a lot of the 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 the Student's t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun. If bias is found, either its cause must be found and corrected or the purchaser and supplier must agree to interpret future test results in light of the known bias.