If a Customer is buying an Air-Conditioner, will he inform the Manufacturer that the Air-Conditioner should give a cooling of 16 to 22 degree Celsius? If he is buying a Car, will he ever inform the Manufacturer that he needs a car that has a mileage of 42 km per liter?
As you can see, the Customer Requirements are always hazy. Although the Customer may think he Knows What he Wants, he Does not have the Technical or Engineering Specifications of Communicating exactly What he Wants. This conversion of Customer Requirements into Technical or Engineering Specifications is the job of this tool: The Quality Function Deployment (popularly known as QFD). QFD is a unique tool and has a structured approach to identify these requirements. Due to its complexity, this tool is generally only used in Six Sigma Black Belt Projects. Although, I have seen a few Green Belts use this tool in their Six Sigma projects too. There is also enough scope of using this tool as a standalone technique without being dependent on a Six Sigma project.