需要引用Nuget包 MathNet . Numerics

公式

Minitab 合并标准差公式说明

https://support.minitab.com/zh-cn/minitab/18/help-and-how-to/quality-and-process-improvement/control-charts/how-to/variables-charts-for-subgroups/i-mr-r-s-chart/methods-and-formulas/estimating-sigma-for-the-r-chart-or-the-s-chart/#pooled-standard-deviation-method

代码