# Six Sigma

Six Sigma describes a measure of quality that reflects a goal of near perfection. The Six Sigma Way is a disciplined, data-driven approach and methodology for eliminating defects and improving quality. Six Sigma is a statistical term that, in effect, translates as “near perfection.” A Six Sigma goal means the product is 99.9997 percent defect free (68 percent = 2 Sigma; 93 percent = 3 Sigma, 99.4 percent= 4 Sigma; 99.5 percent= 5 Sigma). Sigma means standard deviation which is a statistical term that describes how much variation exists in a set of data. Thus, we may set a goal of 3-second response time for a certain category of query. Striving for Six Sigma quality would mean that if we measure response time for 10,000 queries, we want to find that 9,997 of those queries would meet the goal of a response time of 3 seconds or less. (Actually, we usually speak in terms of a million opportunities (i.e., queries). So, the definition is not quite accurate. There are also other aspects to the measurement process – i.e., short-term versus long-term variations in the data, etc. However, the basic principle is to strive for a near perfect product.)