Check Tests & Retests

When test results are questioned by the trade, AWTA Ltd has a policy to conduct check tests and retests. The procedures are well defined in the IWTO Regulations.

Because of the inherent variation, a check test will normally give a slightly different answer to the original test even if no “error” exists. Provided it falls within a statistically based Maximum Retest Range, defined by IWTO, the original and check test data are combined and reissued. No error has occurred in this situation. When a check test or retest exceeds the Maximum Retest Range, an error is acknowledged. This may be obvious, or resolved with additional sampling and/or testing. A new result without the original data is issued.

For information, the IWTO Maximum Retest Ranges for Wool Base, VM Base, Mean Fibre Diameter, Colour, Staple Length and Staple Strength are shown in Column B of Table 1.

The key rule for retests, check tests or recore check tests is that if the extra data is compatible, ie. the difference falls within the Maximum Retest Range, then the additional data are combined with the original data and becomes the new result. If the data exceeds the Maximum Retest Range, ie. an error has deemed to have occurred, then the original result is withdrawn and the new data issued as the result.

While attention often focuses on individual errors, only 0.2% of AWTA Ltd Certificate results are requested to be checked by the trade. Only 0.02% of all Certificate results are found to be in error.