Minitab动画教程

标准差估计方法采用Minitab选用的“合并标准差”，该方法计算出来的西格玛更严格，但相应的Cpk值将会降低（感谢QQ里的Minitab学习群里的“树上右从”兄无私的解答，When the subgroup size is greater than 1, Minitab uses the Pooled standard deviation over the Rbar method for estimating the standard deviation because the relative efficiency of using the range instead of the pooled standard deviation decreases as the subgroup size increases (the range uses only the minimum and maximum values in the subgroup, and the standard deviation uses all of the data). The relative efficiency of the range method compared to s (the sample standard deviation) is shown here for various sample sizs: n Relative Efficiency
2 1.000
3 0.992
4 0.975
5 0.955
6 0.930
10 0.850
From Montgomery 2005, 95-96.
Montgomery 2005, 95 states, "Using the range to estimate dates from the earliest days of statistical quality control, and it was popular because it is very simple to calculate. With modern calculators and computers, this isn't a major consideration today. Generally, the "quadratic estimator" based on s is preferable."
Reference: D.C. Montgomery (2005). Introduction to Statistical Quality Control, Fifth Edition. John Wiley & Sons, Inc.)
同时，增加了新增子组数据时，Xbar-R自动更新功能的演示。
如各位同仁有不同意见，可以在回帖中指出，大家共同学习。