Six Sigma Defined and Explained

The basis of Six Sigma is measuring a process in terms of defects. The statistical concept of six sigma means your processes are working nearly perfectly, delivering only 3.4 defects per million opportunities (DPMO). As you know from your experience with Six Sigma, Sigma (the Greek letter σ) is a statistical term that measures standard deviation. In the context of management, it’s used to measure defects in the outputs of a process and show how far the process deviates from perfection. (We’ll get into the statistics in later chapters.) A one-sigma process produces 691462.5 defects per million opportunities, which translates to a percentage of satisfactory outputs of only 30.854%. That’s obviously really poor performance. If we have processes functioning at a three sigma level, this means we’re producing 66807.2 errors per million opportuσ Sigma (σ) A term used in statistics to represent standard deviation, an indicator of the degree of variation in a set of measurements or a process. A one-sigma process produces 691462.5 defects per million opportunities—a percentage of satisfactory outputs of only 30.854%. Standard deviation A measure of the spread of data points in relation to the mean. It’s the most common measure of variation in a set of data. Six Sigma A philosophy of managing that focuses on eliminating defects through practices that emphasize understanding, measuring, and improving processes. It’s based on the statistical concept of six sigma, measuring a process at only 3.4 defects per million opportunities (DPMO). Defect A measurable characteristic of the process or its output that is not within the acceptable customer limits, i.e., not conforming to specifications.The sigma level of a process is calculated in terms of defects per million opportunities (DPMO).