Ishikawa's biggest contribution is in simplifying statistical techniques for quality control in industry. At the simplest technical level, his work has emphasised good data collection and presentation, the use of Pareto Diagrams to prioritise quality improvements and Ishikawa Diagrams.
Ishikawa sees the Cause-and-Effect Diagram (or Ishikawa Diagram), like other tools, as a device to assist groups or quality circles in quality improvement. As such, he emphasises open group communication as critical to the construction of the diagrams. Ishikawa diagrams are useful as systematic tools for finding, sorting out and documenting the causes of variation of quality in production and organising mutual relationships between them. Other techniques Ishikawa has emphasised include the seven Quality Control tools.
Other than technical contributions to quality, Ishikawa is associated with the Company-wide Quality Control (CWQC) Movement that started in Japan during the period 1955--60 following the visits of Deming and Juran. Ishikawa sees the CWQC as implying that quality does not only mean the quality of product, but also of after sales service, quality of management, the company itself and the human life. The outcomes of such an approach are: