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Six-Sigma emerged in the 1980s in response to an increasing demand for quality and reliable products and services with low rate of defects. In 1990s Six Sigma was registered as trademark and service mark of Motorola, Inc., for an approach to business process quality improvement that seeks to find and eliminate causes of defects and errors, reduce cycle times, reduce cost of operations, improve productivity, achieve higher asset utilization and improve customer satisfactions (Barney, Matt, 2002).
Some authors define Six Sigma as a managerial strategy aimed at improving organizational processes, products and services and broadly directed to customers’ satisfaction. Some of the constructs of the Six Sigma model resemble those of Total Quality Management (TQM): meeting customers’ needs, disciplined use of real facts, statistical data and checking, strong support from the company leaders, and continuing improvement (Pinto et al., 2008). Six-Sigma does not regard quality in its traditional sense, i.e. compliance with standards and company internal requirements. Rather, it defines quality as the value added by a vast productive effort that aims at reaching the strategic objectives planned by a company (Pfeifer et al., 2004; Wolek, 2004).
Six-Sigma encompasses a statistical thinking, typical of the past, with emphasis on quality control and problem solving. However, Six Sigma’s systematic use of statistical tools through a cycle known as define-measure-analyze-improve-control (DMAIC), leads to a cycle called plan-do-check-action (PDCA) (Pande et al., 2001). In fact, Six Sigma goes beyond statistical thinking.
Many authors recognize the difficulty of defining the constructs and boundaries of Six Sigma but emphasize that the program has singular aspects with respect to other quality management approaches (Klefsjo¨ et al., 2001; McAdam and Lafferty, 2004; Llore´ns-Montes and Molina, 2006; Schroeder et al., 2008; Ahmed and Abonamah, 2013; Linderman et al., 2003; Choo et al., 2007).
The first Six Sigma quality improvement model as applied by Robert Galvin at Motorola, Inc. refers to the following five step process of problem solving approach, also known as DMAIC:(Define, Measure, Analyze, Improve, and Control) originally developed by Deming in early 1960s as listed below:
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Define: This step defines who the customers are, what the customers want, the process capabilities, and provides objectives for project-based improvement efforts;
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Measure: This step measures the quality characteristics that reflects improvement in customer satisfaction and product performance and provides the metrics of data on which the improvement efforts will be based upon;
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Analyze: In this step, data collected in pervious steps are analyzed using analytical tools such as Pareto analysis, process flow diagram, fish-bone diagram, statistical process control charts, for identifying necessary design and process modifications for achieving customer satisfaction and performance objectives;
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Improve: In this step resources are allocated so that design and process modifications needed for improvement can be implemented;
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Control: In this step the process is monitored using quality management tools such as Pareto charts, and statistical process control charts to ensure that the performance improvements are maintained.