5.1 This test measures an important property to users of sew through flange buttons. This is a means of determining the resistance of the bridge of the button to a strain which can cause it to fall off a garment to which it is attached.

5.2 If there are differences of practical significance between the 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, test samples should be used that are as homogeneous as possible, that are drawn from the material from which the disparate test results were obtained, and that are randomly assigned in equal numbers to each laboratory for testing, Other materials with established test values may be used for this purpose. The test results for 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.