Consider a k-sigma process.

a. If k = 4, determine the fraction of all parts that meet specifications and calculate Cp. Now suppose that a car consists of 1000 parts, each of which is governed by a 4-sigma process. What fraction of all cars will be perfect (meaning all 1000 parts meet specs)?

b. Repeat part a for a 6-sigma process. Now can you see why companies like Motorola are not satisfied with anything less than a 6-sigma process?