Where the statement comes from that" the shift of process in long term is 1.5σ"
Motorola has determined, through years of process and data collection, that processes vary and drift over time - what they call the Long-Term Dynamic Mean Variation. This variation typically falls between 1.4 and 1.6.
You can refer to the book published by Motorola ,entitled "Six Sigma Producibility Analysis and Process Characterization", written by Mikel J. Harry and J. Ronald Lawson.
RSS Feed
10 个回复
Jasonchen (威望:0)
赞同来自:
- Where the statement comes from that" the shift of process in long term is 1.5σ"
Motorola has determined, through years of process and data collection, that processes vary and drift over time - what they call the Long-Term Dynamic Mean Variation. This variation typically falls between 1.4 and 1.6.You can refer to the book published by Motorola ,entitled "Six Sigma Producibility Analysis and Process Characterization", written by Mikel J. Harry and J. Ronald Lawson.
2.我的看法是：既然能得出1.5这个相对比较精确的数字，不管是制造业分析还是经验，总有个推算或计算的过程，总不至于是拍脑瓜灵机一动想出来的吧！
张驰如何算的我不知道，其实在计算一个过程的SIGMA质量水平时所说的1.5个SIGMA的移动，就是考虑均值的变异，可以用T分布衡量，只是样本大小根据管制图经验N=3-5，所以取N=4，alpha=0.05时便可求得平均值正负1.5SIGMA的移动范围。这是我的推算，详见：
http://www.6sq.net/cdb/viewthread.php?tid=912