what is sigma in quality
It is a statistical variation with reference to original
±1σ 68.2689%
±2σ 95.45%
±3σ 99.73%
±4σ 99.99367%
±5σ99.9999427%
±6σ 100-1.973 × 10-7%
±7σ 100-2.5596 × 10-10%
±8σ 100-1.24419 × 10-13%
±9σ 100-2.25718 × 10-17%
±10σ 100-1.53398 x 10-21%
normally 3 sigma is the mostly used industry standard