Purpose -The purpose of this paper is to assess Lean Six Sigma to identify important advances over the last ten to 15 years and discuss emerging trends that suggest how the methodology needs to evolve. The goal is to aid those who want to use the method to improve performance as well as assist those developing improvement methodologies. Design/methodology/approach -The use and development of Lean Six Sigma is reviewed including the origins of the method, the what, why and benefits of the method, how the approach is different, the integration of Lean and Six Sigma, implementation mistakes made, lessons learned and developments needed in the future. Findings -It is found that organizations have many different improvement needs that require the objectives and methods contained in the lean and Six Sigma methodologies. It is also found that deployment and sustaining improvements are major issues that can be overcome by building a sustaining infrastructure and making improvement a business process. Critical issues include using Lean Six Sigma to generate cash in difficult economic times, development of data-based process management systems and the use of working on improvement as a leadership development tool. Practical implications -These findings suggest that improvement is most effective when approached in an holistic manner addressing improvement in all parts of the organization using a holistic improvement methodology such as Lean Six Sigma. Improvement must address the flow of information and materials thorough processes as well as the enhancement of value-adding process steps that create the product for the customer. This leads naturally to making improvement a business process that is planned for, operated and reviewed as any other important business process is. Originality/value -The roadmaps, guiding principles, and deployment pitfalls identified will be of value to those initiating and operating improvement processes in their organizations enabling them to rapidly create useful and sustainable improvements. The discussion of needed enhancements will be of value to those who are working to improve the effectiveness of the approach.

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Methods to determine the validity of regression models include comparison of model predictions and coefficients with theory, collection of new data to check model predictions. comparison of results with theoretical model calculations, and data splitting or cross-validation in which a portion of the data is used to esrimarr the model coefficients. and the remainder 01 the data is used to measure theprediction accuracy of the model. An expository review of these methods is presented. It is concluded that data splitting is an effective method of model validation when it is not practical to collect new data to test the model. The DUPLEX algorithm, developed by R. W. Kennard, is recommended for dividing the data into the estimation set and prediction set when there is no obvious variable such as time to use as a basis to split the data. Several examples are included to illustrate the various methods of model validation.

Purpose The purpose of this paper is to share the experiences and perspectives of three practitioners from two continents on the subject of Lean Six Sigma (LSS) from both academic and industrial viewpoints. The authors of the paper have each been working on the topic of LSS over the past 15 years and have contributed over 150 journal and conference papers to the topics of lean and Six Sigma. Design/methodology/approach The approach is to synthesize the practical experiences and research conducted by three authorities on the topic of LSS. In addition, relevant secondary data have also been used in the sections where and when appropriate. Findings The authors initially present the history of LSS emphasizing the importance of integration of the two most effective process excellence methodologies over the past 30 years. The authors also report the current trends of LSS in organizations as well as the emerging future trends. They argue that LSS will continue to grow and evolve across the globe for several years. Practical implications The paper is intended to be equally useful to both academics and practitioners who are interested on the topic of LSS. From a pure practical standpoint, the paper provides an overview of the past, present and future trends of LSS as a powerful business strategy and problem-solving methodology for all industrial sectors, irrespective of their size and nature. The documentation of the history and recent developments in LSS should be useful to researchers in academia. Originality/value In authors’ best knowledge, there are no recent journal articles which cover all the three of these aspects; the past, the present and the future of LSS. This paper presents the above three aspects in a unique manner and addresses the gap between the current state and future directions of LSS.