Today, an organization’s ability to compete in changing global economy depends largely on the quality of products and services. Trends such as supply base reduction and consolidation, product and process design, production or manufacturing planning are increasing. For many companies, purchase accounts for 50% to 60% of sales amount and are the source of half of the quality problems. Process capability analysis is a vital part of an overall quality improvement program. It is a technique that has application in many segments of the product cycle, including product and process design, vendor sourcing, production or manufacturing planning, and manufacturing, Douglas C. Montgomery (2001). Frequently, a process capability study involves observing a quality characteristic of the product. Since this information usually pertains to the product rather than the process, this analysis should strictly speaking be called a product analysis study. A true process capability study in this context would involve collecting data that relates to process parameters so that remedial actions can be identified on a timely basis.