Walter A. Shewhart was a physicist and statistician at western-electric-bell-laboratories who created statistical process control (SPC) in the 1920s and 1930s. His work on control charts and the distinction between common-cause and special-cause variation laid the foundation for modern quality management. Shewhart's 1931 book Economic Control of Quality of Manufactured Product remains a foundational text.
Deming met Shewhart in the late 1920s and considered him his most important intellectual influence. The relationship was both professional and personal — Deming edited Shewhart's 1939 book Statistical Method from the Viewpoint of Quality Control and spent years trying to make Shewhart's dense statistical writing accessible to a broader audience. Deming frequently credited Shewhart in his lectures and writings, always insisting that his own contributions built on Shewhart's foundations.
Deming's PDSA (Plan-Do-Study-Act) cycle is explicitly adapted from Shewhart's specification-production-inspection cycle, which Shewhart first described in the 1930s. Deming always called it the "Shewhart Cycle" in recognition of its origins. Rafael Aguayo's dr-deming-the-american-who-taught-the-japanese-about-quality provides a detailed account of the Shewhart-Deming intellectual relationship and how Shewhart's statistical foundations were transmitted through Deming to the world. The conceptual leap from inspection-based quality control to process-based quality management — the idea that quality must be built in, not inspected in — traces directly to Shewhart's statistical framework.
Shewhart's influence extends through Deming to the entire quality movement, including juse-union-of-japanese-scientists-and-engineers, toyota-motor-corporation, and the lean manufacturing tradition pioneered by taiichi-ohno. Without Shewhart's statistical foundations, Deming's system of profound knowledge would lack its empirical backbone.