On the basis of the aim characteristic values of the experimental results three control lines of statistics were designed a central line a upper control limit a lower control limit in right angle coordinates .

此法是在平面座标系中，根据试验结果的目标特性值， 绘出三条具有统计意义的 控制线。

Based on the hypothesis of Xbar-R control chart the type II error (β risk ) of Xbar-R control chart was studied when the Sample 's mean at time t lied in different positions between upper control limit and lower control limit of Xbar-R chart .

从Xbar-R控制图的假设检验问题出发，研究了t时刻样本均值（ Xbar）和极差（R）处于 控制 限内不同位置时，Xbar-R控制图假设检验的第二类错误（β风险）问题。