应用Empower Stats软件分析阈值效应

The analysis of threshold effect using Empower Stats software

生物医学研究中许多研究因素在一定范围内对结果变量无影响或有正效作用,超过某一阈值后,作用大小或/和方向可发生变化,称为阈值效应.在分析研究因素（x）对结果变量（y）的作用有无阈值效应时,可先通过平滑曲线拟合观察是否有分段线性关系,然后采用分段回归模.型、LRT检验和Bootstrap重抽样法进行阈值效应分析.美国X＆Y Solutions软件公司开发的Empower Stats软件,设有阈值效应分析模块,可输入阈值后按所给阈值分段模拟数据,也可以不输入阈值,由软件自动确定最佳阈值模拟数据,并计算阈值置信区间.

In many studies about biomedical research factors influence on the outcome variable,it has no influence or has a positive effect within a certain range.Exceeding a certain threshold value,the size of the effect and/or orientation will change,which called threshold effect.Whether there are threshold effects in the analysis of factors （x） on the outcome variable （y）,it can be observed through a smooth curve fitting to see whether there is a piecewise linear relationship.And then using segmented regression model,LRT test and Bootstrap resampling method to analyze the threshold effect.Empower Stats software developed by American X ＆ Y Solutions Inc has a threshold effect analysis module.You can input the threshold value at a given threshold segmentation simulated data.You may not input the threshold,but determined the optimal threshold analog data by the software automatically,and calculated the threshold confidence intervals.