Process capability index

Process capability index is a number that shows how well a process is able to meet customer needs. Imagine a factory makes toy cars. The customer wants the cars to be 4 inches long. The process capability index is a number that shows us how close the cars are to being 4 inches long. A process capability index of 1 means that all of the cars are exactly 4 inches long. A process capability index of 0.5 means that all of the cars are between 3.5 and 4.5 inches long. The higher the process capability index, the closer the cars are to being 4 inches long.