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Sampling Wool Clips for Clean Yield by the Core Boring Method¹

Montana Agricultural Experiment Station

Abstract

The core boring method of Wollner and Tanner (1941) was used to sample the clean yield of a wool clip representing about 2700 fleeces which were graded and packed into bags. The data consisted of 264 core samples on which individual clean yields were obtained. The intra-grade variance in clean yield of the aged ewe wool and yearling ewe wool is 30.0 and 12.0, respectively. The difference is statistically significant. The number of cores required to represent lots of wool within specified limits of error was calculated from these estimates of variance. For the ewe wool, the sampling error (P = .05) of the mean of 29 cores is equal to 2 percent while 115 cores are required for an error no greater than 1 percent. Only 12 and 46 cores of yearling ewe wool are required for sampling errors no greater than 2 percent and 1 percent, respectively. About 17 percent and 24 percent larger samples of ungraded than graded aged ewe and yearling ewe wool, respectively, would be necessary for the same level of accuracy.

¹ Paper No. 139 Scientific Journal Series of the Montana Agricultural Experiment Station.

² This study is based on data obtained through researches conducted by the Wool Division, Livestock and Meats Branch, Office of Distribution, War Food Administration, in cooperation with the Montana Agricultural Experiment Station. Special thanks are due Mr. Alexander Johnston, formerly field supervisor in charge of coring work at the time these data were collected, and now Chief of the Wool Division, Mr. Warner M. Buck, Marketing Specialist, Mr. George LeCompte, Marketing Specialist, who conducted the laboratory determinations on shrinkage of sample cores, all of the Wool Division, Livestock and Meats Branch, Office of Distribution, War Food Administration, and to Mr. Curtis Hughes, formerly wool specialist at the Montana Agricultural Experiment Station, who assisted in the collection of the data.