Comparer des méthodes

	Carte de contrôle EWMA	Carte de contrôle des variables de Shewhart (X-bar / R)
Domaine	Statistique	Statistique
Famille	Process / pipeline	Process / pipeline
Année d'origine	1959	1931
Auteur d'origine	S. W. Roberts	Walter A. Shewhart
Type	Statistical process control chart for small shifts	Statistical process control chart for variables
Source fondatrice	Roberts, S. W. (1959). Control chart tests based on geometric moving averages. Technometrics, 1(3), 239–250.	Shewhart, W. A. (1931). Economic Control of Quality of Manufactured Product. D. Van Nostrand Company. ISBN: 978-0-87389-076-2
Alias	exponentially weighted moving average chart, EWMA control chart, geometric moving average chart, EWMA kontrol kartı	X-bar and R chart, Shewhart chart, variables control chart, process control chart
Apparentées	3	4
Résumé	The exponentially weighted moving average (EWMA) control chart, introduced by S. W. Roberts in 1959, monitors a process using a weighted average that gives the most recent observation the greatest weight while letting older observations fade geometrically. Like CUSUM, this memory makes it highly effective at detecting small, sustained shifts in the process mean, with a single smoothing parameter λ controlling how much past information the chart retains.	The Shewhart control chart, invented by Walter Shewhart at Bell Labs in the 1920s and set out in his 1931 book, is the foundational tool of statistical process control. It plots a process statistic — typically the subgroup mean (X-bar) and range (R) — over time against a center line and three-sigma control limits, distinguishing the natural common-cause variation inherent in a stable process from special-cause variation that signals something has changed and warrants investigation.