The Precision of Dark and Medullated Fibre Testing of Noil

Abstract

The benzyl alcohol test for dark and medullated fibres, developed by AWTA/AWI/CSIRO, was used to estimate the levels of dark and medullated fibres in noil. Variance estimates have been used to estimate the precision of a dark and medullated fibre test at different levels.

Samples used in this study were generated from an earlier trial reported to IWTO, by placing Merino ewes in controlled contact with Damara crossbred lambs. Processing lots generated from this material were converted to top, with all the waste generated during processing being collected for later analysis.

Confidence limits for the measurement of dark and medullated fibre from the front-box noil using the benzyl alcohol method were measured and form the basis of this report.

Analysis of the variance components within the noil measurements showed that the confidence limits of the measurement result increased linearly with the level of dark or medullated fibres. Furthermore, at low dark fibre levels the between-subsample variance was greater than that for between-operator variance while at high levels the between-subsample variance was smaller than that for between-operator. 

Citation

"The Precision of Dark and Medullated Fibre Testing of Noil", V.E. Fish, M.R. Fleet, A.R. Alaya-ay & T.J. Mahar, Report SG01,Sliver Group, IWTO Congress, Xi'an, November 2006