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在低水平放射性测量中,建议采用负二项式分布代替泊松分布来描述真实测量计数的几率分布。从实际测量中估计出计数效率起伏的相对标准偏差。对于负二项式分布,方差-计数平均值之比大于1,以此为基础推导出有关探测限的新公式,并给出一套以本底计数率、测量时间、计数效率起伏的相对标准偏差和单边置信因子为参数的探测限实用曲线。
In low-level radiometric measurements, it is advisable to use negative binomial distribution instead of Poisson distribution to describe the probability distribution of true measured counts. From the actual measurement to estimate the relative standard deviation of counting efficiency fluctuations. For the negative binomial distribution, the ratio of the variance to the average of the counts is greater than 1, on the basis of which a new formula for the detection limit is deduced and a set of relative standards of floor count rate, measurement time, count efficiency fluctuation Deviation and unilateral confidence factors for the parameters of the detection limit utility curve.