Abstract This paper examines the hypothesis that the manual selection of rocks for inspection, testing or analysis is invariably biased towards the heavier (larger) particles in the population being sampled. If the property of interest, such as assay or breakage potential, is size-related then such a bias would lead to systematic errors in the estimation of this property. To test the hypothesis, human volunteers were asked to select a sample of 10 rocks from a tray of 100 rocks of known weights, with and without a blindfold, in duplicate. This was repeated for a number of different rock size ranges in the range −50 + 19 mm. A statistical analysis of the results confirms the hypothesis that in almost all cases the samples were of larger weight than that expected from the known weight of the population of rocks. The magnitude of the bias depended on conditions but was highest for the widest size range. It is also shown that the volunteers produced different results to each other. The blindfold reduced the bias in the narrow size ranges but increased it for the wide size range. These effects are likely to be less important for populations of narrow size range, but where a truly unbiased sample is required strategies are proposed using randomisation processes. Relying on unmoderated human selection will lead to samples which overestimate the weight of the population.

中文翻译：

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人工采样岩石颗粒的偏差

摘要 本文检验了以下假设：人工选择用于检查、测试或分析的岩石总是偏向于采样总体中较重（较大）的颗粒。如果感兴趣的特性，例如化验或破损潜力，是与尺寸相关的，那么这种偏差将导致对该特性估计的系统误差。为了验证这个假设，人类志愿者被要求从一盘 100 块已知重量的岩石中选择 10 块岩石样本，蒙眼和不蒙眼，一式两份。对-50 + 19 mm 范围内的许多不同岩石尺寸范围重复此操作。结果的统计分析证实了这样的假设，即在几乎所有情况下，样本的重量都大于岩石群已知重量的预期重量。偏差的大小取决于条件，但在最宽的尺寸范围内最高。还表明志愿者彼此产生了不同的结果。眼罩减少了窄尺寸范围内的偏差，但增加了宽尺寸范围内的偏差。对于规模范围较小的群体，这些影响可能不太重要，但在需要真正无偏见的样本的情况下，建议使用随机化过程的策略。依赖无节制的人类选择将导致样本高估人口的权重。对于规模范围较小的群体，这些影响可能不太重要，但在需要真正无偏见的样本的情况下，建议使用随机化过程的策略。依赖无节制的人类选择将导致样本高估人口的权重。对于规模范围较小的群体，这些影响可能不太重要，但在需要真正无偏见的样本的情况下，建议使用随机化过程的策略。依赖无节制的人类选择将导致样本高估人口的权重。