What is the simple / very clear definition of the six sigma? What six sigma gives to the business?

Six Sigma is a set of tools that enables you to reduce variation in your process. There are two distinct terms in this nomenclature : "Six" and "Sigma". Sigma is a statistical term used to denote standard deviation, or in simple terms the variation amongst data points. Six refers to Z-Value or how many "Sigmas" can be incorporated between mean and any other reference point on the frequency distribution. The aim of any Six Sigma project typically is to reduce "Sigma" and increase Z-Value. The ideal state for any process is to operate at a Z Value of 6. Practically it would mean there are no more than 3.4 defects per 1 million opportunities in my process.

.Sigma A term used in statistics that measures standard deviation. In business, it is an indication of defects in the outputs of a process and how far these outputs deviate from perfection.

 Six Sigma A statistical concept that measures a process in terms of defects. At the six sigma level, there are only 3.4 defects per million opportunities. Six Sigma is also a philosophy of managing that focuses on eliminating defects through practices that emphasize understanding, measuring, and improving processes. 

The six sigma gives to the business:

·         Inventory levels

·         Aging of inventory

·         Profits and losses

·         Cost of goods or services sold

·         Return on investment