在过程能力分析中,过程能力指数计算通常采用样本级差或者样本标准差来估计过程输出的标准差。实际制造过程中。一些过程输出存在自相关特性。在时间序列理论中的稳定随机过程模型的基础上,通过仿真的方法研究了过程输出存在自相关特性时,传统统计过程控制抽样和标准差估计方法以及样本含量对过程能力指数计算的影响,指出必须考虑过程输出的相关性。并通过实例进行了说明。
The deviation of process output is usually estimated through the range or deviation of the sub - samples in the calculation of Process Capability Index. There are autocorrelation in many practical process outputs. Based on the several stationary stochastic process models of the time- series analysis, the effects of the sampling method, sub -sample size and deviation estimating methods in standard statistical process control are analyzed via simulation in process capability analysis. The necessary of testing autocorrelation of process and proper analysis procedure and methods are set up for the situation.