标题: 双边规格CNpk信赖下界复式抽样计算方法
Bootstrap Lower Confidence Bound for Non-Normal Two-Sided Process Based on Capability Index CNpk
作者: 萧依芳
Hsiao, I-Fang
彭文理
Pearn, W. L.
工业工程与管理系所
关键字: 双边规格;制程能力指标;非常态制程;信赖下界;复式抽样法;Two-sided;Process capability index;non-normal process;lower confidence bound;bootstrap
公开日期: 2012
摘要: 制程能力指标广泛地被用来评估制程产出产品是否符合规格的重要工具,不仅能提供品质保证,也是提供品质改善方面的一个方针。其中又以双边规格Cpk指标在制造业中使用最多、最广泛的指标。但Cpk仅于制程资料服从常态分配时适用,本篇研究考虑Pearn and Chen(1997)提出之CNpk指标,能够在制程资料为非常态分配时也能精确的评估制程良率,然而该指标估计式的抽样分配不易求得,因此,本篇研究应用复式抽样法建构出指标之四种信赖下界,并利用校正因子D来改善样本分配,提出一新估计量进行求算,最后比较在不同的参数变化下四种信赖下界之涵盖率,模拟结果显示,bootstrap-t方法较其他方法为佳,即其涵盖率与预先要求之信赖水准最为接近。
The process capability indices (PCIs) have been extensively used to measure whether the process meets the specifications and they provide quality assurance and guide a principal for quality improvement at the same time. Cpk is the most popular index used in the manufacturing industry. However, Cpk is only appropriate for process under normal distribution. Pearn and Chen (1997) proposed the capability index CNpk for non-normal process. However the exact sampling distribution of CNpk is mathematically intractable. Thus, in this paper, we apply bootstrap methods to construct four lower confidence bound methods of the index. We also modify the sample percentile deviation by a correction factor, called D, and we propose a new estimator to calculate process capability. Under different parameter setting, we compare the coverage rates of the four lower confidence bound methods, and the simulation results showed that bootstrap-t method outperformed the other methods since its coverage rate and pre-determined confidence level is closest.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT070053329
http://hdl.handle.net/11536/71425
显示于类别:Thesis