Statistical Quality Control (SQC) and Six Sigma Methodology: An Application of X-Bar Chart on Kuwait Petroleum Company

Abstract

An x-bar chart is a statistical device used for the study and control of a process. Control charts based on the three sigma limits were produced and have been used effectively for a long time. In today’s developed and developing countries, companies have introduced Six Sigma initiatives in their manufacturing processes which results in fewer defects, and identifies the causes of process variations. Companies employing Six Sigma initiatives are expected to produce 3.4 or less defects per million opportunities (DPMO) using the control limits suggested by Shewhart; then no point will fall outside the control boundaries because of reduction in variation. In this paper an attempt is made to construct a Six Sigma based on data collected from a petroleum company in Kuwait to produce an x-bar chart. Unfortunately, it seems there are some serious deficiencies in the production process since the value of Cp and Cpk are less than 1 which means the process is not capable of meeting its specifications.