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Significance and Use
5.4 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, the test samples to be used are as homogeneous as possible, are drawn from the material from which the disparate test results were obtained, and are randomly assigned in equal numbers to each laboratory for testing. Other fabrics 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.
5.5 Bow or skew can be induced during fabric manufacturing, dyeing, tentering, finishing, or other operations where a potential exists for uneven distribution of tensions across the fabric width. Bow and skew are more visually displeasing in colored, patterned fabrics such as plaids and horizontal stripes rather than in solid colors because the contrast makes the distortion more prominent. These defects may cause sewing problems in such fabrics and draping problems in finished products. Wavy or sharp breaks in the bow line are more detrimental to the appearance of small specimens of a sewn assembly.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D123 Terminology Relating to Textiles
D1776 Practice for Conditioning and Testing Textiles
D3882 Test Method for Bow and Skew in Woven and Knitted Fabrics
D3990 Terminology Relating to Fabric Defects
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ICS Number Code 59.080.30 (Textile fabrics)
UNSPSC Code 11160000(Fabrics and leather materials)
ASTM D7811-13, Standard Test Method for Bow and Skew Using a Measuring Tool, ASTM International, West Conshohocken, PA, 2013, www.astm.orgBack to Top