# Six Sigma

#### What is Six Sigma?

Six Sigma is a data-driven approach to quality improvement that aims to reduce defects and variations in processes, products, or services by identifying and eliminating root causes of problems. It uses a set of tools and techniques to analyze and improve the performance of a process, with the goal of achieving near-perfect quality.The term “Sigma” refers to the Greek letter σ (sigma), which is used to represent the standard deviation of a normal distribution. In Six Sigma, each sigma represents a specific level of quality performance:

- 1 sigma: 68% of the population falls within one standard deviation of the mean
- 2 sigmas: - 4% of the population falls within two standard deviations of the mean
- 3 sigmas: - 7% of the population falls within three standard deviations of the mean
- 4 sigmas: - 994% of the population falls within four standard deviations of the mean
- 5 sigmas: - 99964% of the population falls within five standard deviations of the mean
- 6 sigmas: - 99875% of the population falls within six standard deviations of the mean

In Six Sigma, the goal is to achieve a quality performance level of - 4 defects per million opportunities (DPMO), which is equivalent to a - 73% defect-free rate.

The Six Sigma methodology involves five key steps:

**Define**: Define the problem or opportunity for improvement and establish clear goals and objectives.**Measure**: Collect data to understand the current process and identify areas for improvement.**Analyze**: Analyze the data to identify the root causes of problems and opportunities for improvement.**Improve**: Implement changes to improve the process and reduce defects or variations.**Control**: Monitor and control the improved process to ensure that it remains stable over time.

Six Sigma is often associated with the following tools and techniques:

- Statistical Process Control (SPC)
- Design of Experiments (DOE)
- Failure Modes and Effects Analysis (FMEA)
- Root Cause Analysis (RCA)
- Flowcharts
- Histograms
- Scatter plots

The Six Sigma methodology has been widely adopted in various industries, including manufacturing, healthcare, finance, and government. It is often used to improve quality, reduce costs, and increase customer satisfaction.

There are two main levels of certification in Six Sigma:

**White Belt**: Basic understanding of the Six Sigma principles and terminology.**Black Belt**: Advanced training and certification for individuals who will lead and manage Six Sigma projects.

Green Belts are also recognized as a level of certification, which is typically considered an intermediate level between White and Black Belts.