论文标题

计数数据分析中的多项式,泊松和高斯统计数据

Multinomial, Poisson and Gaussian statistics in count data analysis

论文作者

Lassa, Jakob, Bøggild, Magnus Egede, Hedegård, Per, Lefmann, Kim

论文摘要

通常,众所周知,计数统计量未通过高斯近似正确描述。然而,在中子散射中,将这种近似值应用于计数统计量是普遍的实践。也以低计数数字。我们表明,这种近似值的应用不仅会导致偏斜的结果,例如背景级别估计,而且在两位数计数中的估计数字。实际上,这种近似值在所有计数上都不精确。取而代之的是,引入了多项式方法以及一种更标准的泊松方法,我们将其与高斯案例进行了比较。这两种方法源于对多探测器设置和标准三轴仪器的正确分析。我们设计了一个简单的数学程序,使用多项式分布生成无偏置的拟合,并在合成和实际的无弹性散射数据上证明了这种方法。我们发现多项式方法几乎提供了公正的结果,在某些情况下,典型的统计量优于泊松统计。尽管有很大的偏见,但在拟合模型不是现实的真实表示的情况下,高斯方法通常更强大。因此,用于低计数中子散射的适当数据分析工具箱应包含多个用于计数统计的模型。

It is generally known that counting statistics is not correctly described by a Gaussian approximation. Nevertheless, in neutron scattering, it is common practice to apply this approximation to the counting statistics; also at low counting numbers. We show that the application of this approximation leads to skewed results not only for low-count features, such as background level estimation, but also for its estimation at double-digit count numbers. In effect, this approximation is shown to be imprecise on all levels of count. Instead, a Multinomial approach is introduced as well as a more standard Poisson method, which we compare with the Gaussian case. These two methods originate from a proper analysis of a multi-detector setup and a standard triple axis instrument.We devise a simple mathematical procedure to produce unbiased fits using the Multinomial distribution and demonstrate this method on synthetic and actual inelastic scattering data. We find that the Multinomial method provide almost unbiased results, and in some cases outperforms the Poisson statistics. Although significantly biased, the Gaussian approach is in general more robust in cases where the fitted model is not a true representation of reality. For this reason, a proper data analysis toolbox for low-count neutron scattering should therefore contain more than one model for counting statistics.

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