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In sampling a week's output of 300 wagons of coal in order to estimate the mean ash content, how many visits should be paid to the colliery each week? How many wagons should be sampled on each visit? How many ‘increments’ should be taken from each wagon? What errors are introduced by the techniques of ‘reduction’ and analysis? This article describes some experiments made to provide information on questions such as these, and discusses the application of the results.
Hebden et al. (Sat,) studied this question.