Is Six Sigma worth implementing? Yes, when a process repeats often, its defects cost real money and the data already exists; no when the work is a one-off, the cause is an obvious broken step or the real aim is invention. Almost every disadvantage people list sits on the second side of that line: training time, slow projects, paperwork and a narrow view of quality. This guide prices those costs and shows how organisations reduce them.

Six Sigma grew at Motorola in the 1980s and then spread to other manufacturers and service firms. Its pitch is simple: pick a process, measure its defects, find the causes with data and fix them for good. The pitch is also where the trouble starts, because each word in it (pick, measure, data, for good) is a place where an implementation can go wrong. The old argument of "pros versus cons" is therefore less useful than a sharper question: under which conditions do the pros appear, and what does it cost to create those conditions?
Where does Six Sigma earn its keep?
Six Sigma pays when four conditions hold together. The process runs often enough to produce plenty of observations. Each defect has a price someone can name, such as rework, scrap, refunds or a missed delivery. One person owns the process and can change it. And the cause is not obvious, so analysis adds something that a quick fix would not.
When those conditions are in place, the method brings real strengths that older improvement drives often lacked: