What percentage of process variability does six sigma capture?

Six Sigma is a well-established methodology aimed at improving process efficiency and reducing variability. The term "six sigma" refers to a statistical measure that indicates a process is performing at a high level of quality, specifically with a goal of no more than 3.4 defects per million opportunities. This translates to a process that is operating at a variance that captures approximately 99.99966% of its output within specified limits.

The choice of 88% does not align with the benchmark set by Six Sigma principles. In fact, Six Sigma aims for a much higher capture rate of process performance. Thus, the accurate understanding of Six Sigma is that it captures nearly all variability in processes to the point where process excellence can be achieved, which aligns most closely with the 99% capture rate. By targeting variability reduction to such an extent, organizations can ensure more consistent quality in their product and service delivery, minimizing the risk of defects and rework.

This principle is foundational in the improvement programs that businesses adopt when striving for operational excellence.