Statistical Process Control (SPC) has become a major factor in the reduction of manufacturing process errors over the past years. Sometimes known as the Demming methods for the person that introduced them to Japan and then the United States, they have become necessary tools in quality control processes. Since many of the employees in the manufacturing area have limited background in statistics, a large dependency has been built on the creation of charts and their interpretation. The statistics which underlay these charts are often those we have introduced in previous sections. The unique aspect of SPC is in the presentation of data in the charts themselves.