The business environment has changed a lot during the last decade. Several  hundreds of thousands of businesses worldwide implemented ISO 9000 quality management systems. Many businesses and their suppliers have implemented the Six Sigma methodology. However, the challenge is to improve profitability significantly, to prevent marketplace dynamics such as the dot-com meltdown of 2000. The value of performance measures has become more important than ever.
A business is a collection of processes, including the leadership process. Each   business process has inputs that include suppliers, assets, resources (capital,      material, people), and information. The process also has a vision, measures,      policies and procedures, and output that include products or services for customers. Every business has variances. The question is what to do with them. Each business must have a process to handle excessive variances in the   organization. Typically, these variances are the leaks in profitability. To fine-tune profitability, one must look at measures of all aspects of the organization the way it really works in order to reverse any loss of profitability.

Six Sigma is essentially a comprehensive yet flexible system for achieving, supporting, and maximizing business profits. It is a methodology driven by          understanding customer needs, and the disciplined use of data, facts, and statistical analysis to improve and reinvent organizational processes.

So what does this really mean? How is it deployed? How can it be best employed for maximum advantage within your organization?

Six Sigma is a business management strategy, originally developed by Motorola that today enjoys wide-spread application in many sectors of industry. Six Sigma was originally developed as a set of practices designed to improve manufacturing processes and eliminate defects, but its application was subsequently extended to other types of business processes as well.  In Six Sigma, a defect is defined as      anything that could lead to customer dissatisfaction.

Six Sigma seeks to identify and remove the causes of defects and errors in manufacturing and business process. It uses a set of quality management        methods, including statistical methods, and creates a special infrastructure of   people within the organization ("Black Belts" etc.) who are experts in these    methods. Each Six Sigma project carried out within an organization follows a      defined sequence of steps and has quantified financial targets (cost reduction or profit increase).

»    Origin and meaning of the term "Six Sigma process"
The following outlines the statistical background of the term Six Sigma.

Sigma (the lower-case Greek letter σ) is used to represent the standard deviation (a measure of variation) of a statistical population. The term "six sigma process" comes from the notion that if one has six standard deviations between the mean of a process and the nearest specification limit, there will be practically no items that fail to meet the specifications. This is based on the calculation method        employed in a process capability study.

In a capability study, the number of standard deviations between the process mean and the nearest specification limit is given in sigma units. As process        standard deviation goes up, or the mean of the process moves away from the   center of the tolerance, fewer standard deviations will fit between the mean and the nearest specification limit, decreasing the sigma number.

»    The role of the 1.5 sigma shift

Experience has shown that in the long term, processes usually do not perform as well as they do in the short. As a result, the number of sigmas that will fit between the process mean and the nearest specification limit is likely to drop over time, compared to an initial short-term study. To account for this real-life increase in process variation over time, an empirically-based 1.5 sigma shift is introduced into the calculation. According to this idea, a process that fits six sigmas between the process mean and the nearest specification limit in a short-term study will in the long term only fit 4.5 sigmas – either because the process mean will move over time, or because the long-term standard deviation of the process will be greater than that observed in the short term, or both.

Hence the widely accepted definition of a six sigma process is one that produces 3.4 defective parts per million opportunities (DPMO). This is based on the fact that a process that is normally distributed will have 3.4 parts per million beyond a point that is 4.5 standard deviations above or below the mean (one-sided capability study). So the 3.4 DPMO of a "Six Sigma" process in fact corresponds to 4.5        sigmas, namely 6 sigmas minus the 1.5 sigma shift introduced to account for long-term variation. This is designed to prevent underestimation of the defect levels likely to be encountered in real-life operation.

»    Sigma levels

Taking the 1.5 sigma shift into account, short-term sigma levels correspond to the following long-term DPMO values (one-sided):
One Sigma = 690,000 DPMO = 31% efficiency
Two Sigma = 308,000 DPMO = 69.2% efficiency
Three Sigma = 66,800 DPMO = 93.32% efficiency
Four Sigma = 6,210 DPMO = 99.379% efficiency
Five Sigma = 230 DPMO = 99.977% efficiency
Six Sigma = 3.4 DPMO = 99.9997% efficiency

»    Methodology

Six Sigma has two key methodologies: DMAIC and DMADV, both inspired by Deming’s Plan-Do-Check-Act Cycle. DMAIC is used to improve an existing   business process; DMADV is used to create new product or process designs.

DMADV is also known as DFSS, an abbreviation of "Design For Six Sigma".

»    Implementation Roles
One of the key innovations of Six Sigma is the professionalizing of quality management functions. Prior to Six Sigma, quality management in practice was largely relegated to the production floor and to statisticians in a separate   quality department. Six Sigma borrows material arts ranking terminology to define a  hierarchy (and career path) that cuts across all business functions and a promotion path straight into the executive suite.

»    Quality management tools and methodologies used in Six Sigma
Six Sigma makes use of a great number of established quality management methods that are also used outside of Six Sigma. The following table shows an overview of the main methods used.

- 5 whys
- Analysis of variance
- Anova Gage R & R
- Axiomatic Design
- Business Process Mapping
- Catapult exercise on variability
- Cause & effects diagrams (also known as fishbone or lshikawa diagram)
- Chi-square test of independence and fits
- Control chart
- Correlation
- Cost benefit analysis
- CTQ Tree

- Customer survey through use of Enterprise Feedback Management (EFM) System
- Design of experiments
- Failure mode and effects analysis
- General linear model
- Histograms
- Homogeneity of variance
- Pareto Chart
- Pick Chart
- Process capability
- Regression analysis
- Root cause analysis
- Run Charts
- SIPOC analysis (Suppliers, Inputs, Process, Outputs, Customers)
- Stratification
- Taguchi Methods
- Thought Process Map
- TRIZ

Generally speaking, companies use Six Sigma to reduce variation in products and processes - but the net effect of any Six Sigma project is what people are really looking for: fewer defects, shorter cycle times, increased capacity and throughput, lower costs, higher revenues and reduced capital expenditures.

When Six Sigma is deployed systematically and pervasively - with the right       technology support and leadership force - it can produce large amounts of cash for shorter-term profitability or for longer-term investments.

In its most simple sense, Six Sigma is a highly disciplined approach to decision making that helps people focus on improving processes to make them as near   perfect as possible.

The term "Six Sigma" relates to the number of mathematical defects in a process. Six Sigma practitioners focus on systematically eliminating the defects so they can get as close to "zero defects" as possible.

So Now a day’s all big industrialist and companies are trying to utilize the six sigma strategy by which they can  increase their profit and reduce their cost and also thereby increasing customer base for their product by which they can sustain in the industry as remarkable level and as an achievement of something in terms of  higher profit.