One of the most important recent developments in orchestrating business process improvement and re-engineering (as well as bottom-line profits) is the application of statistical techniques grouped under the heading of "Six Sigma". Six Sigma is nothing more than a statistical range measurement of an acceptably small number of defects in a given situation. Statistical tools are used both to compute this range and to control the numbers of defects. One of the first books to cover this technique in-depth was Breyfogle's "Implementing Six Sigma". Sales of this thorough analysis of the subject have far exceeded expectations and the book has become a classic reference for engineers and others who have to use Six Sigma in their day-to-day jobs.