An outlier problem in the determination of ore grade
Clarke, B.R. and Lewis, T. (1998) An outlier problem in the determination of ore grade. Journal of Applied Statistics, 25 (6). pp. 751-762.
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Data from recordings of ore assays from the Western Australian goldfields provide motivation to devise new tests for outliers when observations are distributed with the same mean but diff ering variances. In the case of equal variances, tests for a single outlier reduce to well-known tests of discordancy. A block discordancy test for k outliers is also described. The question of whether or not one should omit any observation(s) in the calculation of the mean recoverable gold content is addressed in the context of whether or not the data contain outliers, as judged by a normal model for the 'logged' ore assay values. The given data suggest that models with 'logged' values that follow long-tailed approximately normal distributions may be appropriate.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Chemical and Mathematical Science|
|Publisher:||Taylor & Francis|
|Copyright:||© 1998 Carfax Publishing Ltd|
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