He stressed the importance of systems thinking that begins with product designs, prototype testing, proper equipment operations, and accurate process feedback. Juran's seminar also became a part of JUSE's educational programs. By 1991, JUSE had registered over 331,000 quality circles with over 2.5 million participants in its activities. Today, JUSE continues to provide over 200 courses per year, including five executive management courses, ten management courses, and a full range of technical training programs. After collecting statistical data, Ishikawa found that dispersion came from four common causes, as shown in Figure 6.1 .
Materials often differ when sources of supply or size requirements vary.
Equipment or machines also function differently depending on variations in their own parts, and they operate optimally for only part of the time. Processes or work methods have even greater variations. Finally, measurement also varies. All of these variations affect a product's quality. Ishikawa's diagram has lead Japanese firms to focus quality control attention on the improvement of materials, equipment, and processes.