Six Sigma Introduction

six sigma model


What is six sigma?

Sigma ( s ) is Greek letter used to indicate standard deviation

– A sigma level provides a statistical estimation of the the defect (error) rate

– Six sigma relates to 3.4 Defects Per Million Opportunities (DPMO)

2 ways of implementing six sigma

– As a management philosophy, e.g. General Electric

– As a quality tool for problem solving , most of companies are using it in this way

Six Sigma Origins

In 80s, a Motorola engineer found that less than 5% of the products reached the final station without any repair with a big impact on productivity & repair costs

The engineers decided that the traditional way of measuring defect rate (%) is not satisfying, instead to measure defects per million opportunities

Motorola developed this new concept and created the methodology, which named Six Sigma

– As a continuous improvement tools

The results for MOTOROLA up till 2003

Spent $70 million on quality related education

In 1988, won Malcolm Baldrige (the USA quality award)

Productivity increased average of 12% /yr

Cost of quality reduced by more than 84%

99.7% of in-process defects eliminated

$16 billion in manufacturing costs saved

General Electric Six Sigma Deployment

Capacity improvement of 12-18%

Rise in operating margin to 16.7%

$750 million in saving


GE Capital Mortgage Insurance

Cut defects 96%

Claim payments were reduced by $8M, while borrowers were offered alternatives to foreclosure

Reported a 160% increase in new transactions

Normal Distribution Curve

Normal Distribution Curve


Accuracy & Precision

Accuracy & Precision


What’s the difference between accuracy and precision?


Why 3.4 DPMO ( Defect Per Million Opportunity) ?



Measured process may shift by much as 1.5 sigma, resulting in a max DPMO of 3.4

Six Sigma scale

Six Sigma scale



Harvesting the fruits of 6 s

Harvesting the fruits of 6 s


The Six Sigma DMAIC Model


  • Define and scope the project (including deliverables)
  • Define an acceptable project schedule
  • Achieve consensus on project definition


  • Process definition
  • Metric Definition
  • Measure process baseline
  • Evaluate Measurement System


  • Analyze value stream
  • Analyze source of variation
  • Determine process drivers


  • Generate improvement ideas
  • Prioritize improvement opportunities
  • Define new process flow
  • Define & mitigate failure modes
  • Define new process factor levels


  • Maintain improvement
  • Measure realized bottom-line impact
  • Apply the knowledge elsewhere

The Six Sigma Tool Box

SPC/ Engineering process control/ Operational procedures/ control plans/ Training/ Audit


Brainstorming/ Affinity/ Mind mapping/ Benchmark/ FMEA/ DOE/ Six thinking hats technique/ Root cause analysis/ Process decision program chart /


Scatter diagram/ Regression model/ Anova/ Multiple regression/ DOE/ Lean methods/ Value / tream analysis/ Process cycle efficiency/ 5 S/ Setup reduction


Flowcharts/ Process Maps/ SIPOC / Box-Whisker plots / Cause & effect diagram/ Check sheets

Interrelation digraph/Pareto diagram/ Stem & leaf plot/ Gage R&R/ SPC control charts

Histogram/ Process capability


Matrix diagrams/ Work breakdown structure/ Pareto diagram/ Process maps/ Financial analysis

Affinity diagram/ Nominal group technique/ Prioritization matrix/ Project scheduling

Activity network diagram/ Pert analysis/ Gantt chart/ Quality function deployment

How to apply six sigma (general concept)?



case study (call center)

Simple excel sheet for Gage RR