Six Sigma Quality

Most organisations, and indeed most people, believe a performance standard of 95% right is excellent. Statistically, 95% accuracy (yield) equates to approximately three sigma performance. The following examples show a performance of even 95% good is in sufficient and a greater level of performance is required.

3σ (Yield – 93.32%) 4σ (Yield – 99.38%) 6σ (Yield – 99.997%)
Wrong drug prescriptions issued 150 94 3
New born babies dropped by Doctors/Nurses during delivery 112 10 2
Unsafe drinking water 2 hours per month 1 hours per week 5 seconds per year
No television transmission 27 minutes per week 10 minutes per month 4 minutes per year
Short landings at the busiest airport 5 per day 3 per week 1 in 9 years
Incorrect surgical procedures performed in hospitals 1350 per week 520 per month 4 per year
Lost mail articles 66,000 per hour 5910 per hour 35 per day

Although it is ideal, not all processes are required to be performing at six sigma quality. Higher performance has an associated cost and this cost increases exponentially. Organisations have to find a good balance between cost and performance in order to stay competitive in the marketplace. The following figure shows the sigma performance of some common processes we experience in our daily life.