Process control chart 过程控制图 Assignable Graph of sample data plotted over time Cause ariation 60 UCL 40 Mean Process 20 Average ±3G 0 Random 1357911 Variation Time0 20 40 60 1 3 5 7 9 11 X Time 0 20 40 60 1 3 5 7 9 11 X Time Graph of sample data plotted over time Assignable Cause Variation Random Variation Process Average  Mean Process Control Chart 过程控制图 UCL LCL