Ventura County Sheriff's Forensic Services Bureau, 800 S. Victoria Ave., Ventura, CA 93009, United States.
Anal Chim Acta. 2010 Dec 17;683(1):78-83. doi: 10.1016/j.aca.2010.10.011. Epub 2010 Oct 15.
Because sentences for drug possession depend on the mass of the seized drug, testing laboratories must often determine the summed mass of numerous items submitted under a single case. One common practice for this purpose is to continue analyzing and weighing samples until a legal threshold is passed, at which point it is important to inform the court whether the summed mass is significantly above the threshold, or only marginally so. This paper develops a means for estimating the uncertainty of the summed mass for the common situation where the readability, d, of the balance dominates the uncertainty. It is seen that for all sample sizes the uncertainty, UM, is given by the remarkable simple expression UM=(d/2)×[N+SQRT(3N)]+N×CCE, where N is the number of items and CCE is the absolute value of the calibration check error. In most instances, this can be further simplified to UM=N×d.
由于持有毒品的刑期取决于所查获毒品的重量，检测实验室通常必须确定在单一案件下提交的众多物品的总重量。为此，一种常见的做法是继续分析和称重样本，直到达到法定阈值，此时重要的是通知法院总重量是否明显高于阈值，还是仅仅略有超过。本文针对可读性 d 主导不确定性的常见情况，开发了一种估计总重量不确定性的方法。结果表明，对于所有样本大小，不确定性 UM 由以下显著简单的表达式给出：UM=(d/2)×[N+SQRT(3N)]+N×CCE，其中 N 是物品的数量，CCE 是校准检查误差的绝对值。在大多数情况下，这可以进一步简化为 UM=N×d。
