The six sigma methodology aims to reduce the number of mistakes/defects in a manufacturing process and hence the manufacturing costs. Six sigma is the ultimate measure of quality. As firms improve their processes, and move towards the elusive six sigma, they often need to re-design the products, process and services to “design-out” defects and design-in quality. Describes the underlying statistical concepts behind the six sigma methodology and outlines the process of moving towards the realisation of six sigma quality.