DeVore Greggory R
Department of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
Fetal Diagnostic Centers, Pasadena, Tarzana, and Lancaster, California, USA.
J Ultrasound Med. 2017 Mar;36(3):459-473. doi: 10.7863/ultra.16.03025. Epub 2017 Jan 17.
Although Z scores have been reported in the literature, one of the problems for the nonstatistician is understanding the systematic approach used to compute the predicted mean and standard deviation, components of the Z score equation, which may vary as the independent variable changes over time (eg, gestational age). This review focuses on a step-by-step analysis using linear, quadratic, and fractional polynomials to compute the mean and standard deviation as a function of a continuous independent variable. Once the mean and standard deviation are computed, the Z score and centile can be derived and Z score calculators created that enable investigators to implement the results in the laboratory and/or clinical setting.
尽管文献中已报道了Z分数，但对于非统计学家而言，问题之一在于理解用于计算预测均值和标准差的系统方法，这些是Z分数方程的组成部分，它们可能会随着自变量随时间变化（例如胎龄）而有所不同。本综述着重于使用线性、二次和分数多项式进行逐步分析，以计算作为连续自变量函数的均值和标准差。一旦计算出均值和标准差，就可以得出Z分数和百分位数，并创建Z分数计算器，使研究人员能够在实验室和/或临床环境中应用这些结果。
