Six Sigma is a philosophy and systematic methodology for quality improvement. It encourages continuous quality improvement efforts to achieve the ideal goal of 6σ. Sigma(σ) is a statistic representing the standard deviation of the normal distribution, and 6σ level means a level where the tolerance of the specification is six times the standard deviation of the process distribution. In terms of the defective rate, the 6σ level achieves the 0.002 defectives per one million units. However, in the field, the 6σ level is used in the sense of achieving 3.4 defects per one million opportunities, which shows a large gap from the 6σ level in the statistical viewpoint. This is because field practitioners accept a 1.5σ shift of the mean of process when calculating the defective rate under sigma level. It said that the acceptance of 1.5σ shift of the mean is from experience, but there is no research or theoretical explanation to support it logically. Although it is a non-scientific explanation based on experience, considering that there has been no objection to the 1.5σ shift for a long time and it is rather accepted, it is judged that there is a reasonable basis for the 1.5σ shift. Therefore, this study tries to find a reasonable explanation through detective power of control chart via the run-rules to the 1.5σ shift empirically recognized by practitioners.
This research discusses the characteristics and the implementation strategies for two types of quality metrics to analyze innovation effects in six sigma projects: fixed specification type and moving specification type. Zst, Ppk are quality metrics of fixed specification type that are influenced by predetermined specification. In contrast, the quality metrics of moving specification type such as Strictly Standardized Mean Difference(SSMD), Z-Score, F-Statistic and t-Statistic are independent from predetermined specification. Zst sigma level obtains defective rates of Parts Per Million(PPM) and Defects Per Million Opportunities(DPMO). However, the defective rates between different industrial sectors are incomparable due to their own technological inherence. In order to explore relative method to compare defective rates between different industrial sectors, the ratio of specification and natural tolerance called, Ppk, is used. The drawback of this Ppk metric is that it is highly dependent on the specification. The metrics of F-Statistic and t-Statistic identify innovation effect by comparing before-and-after of accuracy and precision. These statistics are not affected by specification, but affected by type of statistical distribution models and sample size. Hence, statistical significance determined by above two statistics cannot give a same conclusion as practical significance. In conclusion, SSMD and Z-Score are the best quality metrics that are uninfluenced by fixed specification, theoretical distribution model and arbitrary sample size. Those metrics also identify the innovation effects for
before-and-after of accuracy and precision. It is beneficial to use SSMD and Z-Score methods along with popular methods of Zst sigma level and Ppk that are commonly employed in six sigma projects. The case studies from national six sigma contest from 2011 to 2012 are proposed and analyzed to provide the guidelines for the usage of quality metrics for quality practitioners.
This paper aims to propose a new steps of hypothesis testing using analysis process and improvement process in the six sigma DMAIC. The six sigma implementation models proposed in this paper consist of six steps. The first step is to establish a research hypothesis by specification directionality and FBP(Falsibility By Popper). The second step is to translate the research hypothesis such as RHAT(Research Hypothesis Absent Type) and RHPT(Research Hypothesis Present Type) into statistical hypothesis such as H0(Null Hypothesis) and H1(Alternative Hypothesis). The third step is to implement statistical hypothesis testing by PBC(Proof By Contradiction) and proper sample size. The fourth step is to interpret the result of statistical hypothesis test. The fifth step is to establish the best conditions of product and process conditions by experimental optimization and interval estimation. The sixth step is to draw a conclusion by considering practical significance and statistical significance. Important for both quality practitioners and academicians, case analysis on six sigma projects with implementation guidelines are provided.
The case company has driven the six sigma innovation programme companywide for the last seven years without any stop in spite of the CEO change. There was neither any benchmark nor the sufficient number of internal experts during the initial stage of driv
In this study, we took the census of the project satisfaction level of the employees who have participated in Six Sigma projects. We divided and measured the project satisfaction by the steps of performing the project (team building, execution, ownership
The paper proposes the misuse types of statistical quality tools according to the kind of data and the number of population in DMAIC process of six sigma. The result presented in this paper can be extended to the QC story 15 steps of QC circle. The study also provides the improvement methods about control chart, measurement system analysis, statistical difference, and practical equivalence.
Six Sigma is widely recognized as a process improvement methodology. In these days, many organizations today are considering how to choose six sigma project. Th is study is to provide six sigma project selection criteria by comparing public corporate with
Many companies desperately effort to find out more effective management method to survive in keen competition. Jack welch of past GE's CEO had said that an excellent result of today's GE management is thanks to Six sigma work. Many korean companies are introduced Six sigma method in their management since late 1993. Six sigma uses a set of strategies, statistics and methods to improve the processes we use to do everything from designing to manufacturing a product from marketing products and services to providing business information to our internal and external customers. The purpose of this study is to overcome these problems and to help make an important decision in establishing introduction strategy by abstracting the reasons and success factors and result indices which are important sources for introducing Six sigma management.
Six sigma has been evolved into three generations. The first generation focused on eliminating or reducing defects as Motorola originally developed and applied. The second generation focused on reducing costs and improving process efficiency as GE extended the first generation. The next generation of six sigma such as D2MAIC(Discovery, Define, Measure, Analyze, Improve, Control) and ICRA(Innovate, Configure, Realize, Attenuate) has been discussed since the beginning of the 21st century. Although the third generation of six sigma emphasizes value creation, but there are few specific tools for its implementation. In this thesis, some tools for finding opportunities for value creation are suggested. It is explained and discussed with examples how the tools can be applied.
After 6 Sigma administration is introduced in domestic in 1997, many corporations are utilizing by survival strategy and method of administration reform. This is applied in all field that this led to R&D from service industry by the next. Success factor
Prior to Six Sigma, many companies had adopted a policy management method designed to manage business performances through the top-down deployment of management policies. This policy management method and the Six Sigma CTQ Flow Down will make a good combination when their merits are developed and systemized as the management innovation program which enables to set up innovation targets along with management targets in the stage of strategic planning and to participate all the personnel from top management down in achieving th targets. This paper will help the companies implementing Six Sigma improve their management constitutions and achieve better management performances through the integration of policy management and Six Sigma.
This paper is to propose new features and models for process innovation after classifying in three categories ; conventional six sigma, lean six sigma and 3rd generation six sigma. First considering two project types which are bottom-up and tod-down, DMAIC process is linked up with QC story 15 steps. Secondly, I present Koreanized lean six sigma model using Japanese production technology and principles. Lastly, this paper also depicts a new 3rd generation six sigma model utilizing MBNQA management quality system.
This paper discusses the relationship between project management and six sigma and the derivation of overall related table. This paper proposes an integrated approach by blending CMM project management and six sigma to meet business goals.