SPC must be practised in 2 phases: The first phase is the initial establishment of the process, statistique descriptive PDF the second phase is the regular production use of the process. An advantage of SPC over other methods of quality control, such as « inspection », is that it emphasizes early detection and prevention of problems, rather than the correction of problems after they have occurred. In addition to reducing waste, SPC can lead to a reduction in the time required to produce the product.
Cette 3e édition enrichie par de nouveaux exercices et d’applications sur tableur Excel, développe les bases de la statistique descriptive : vocabulaire de base ; résumés numériques des variables quantitatives ; indices et concentration ; construction des tableaux ; résumés numériques des variables bidimensionnelles ; moindres carrés ordinaires ; qualité des ajustements ; séries chronologiques ; correction des variations saisonnières.
SPC makes it less likely the finished product will need to be reworked or scrapped. SPC was pioneered by Walter A. Shewhart at Bell Laboratories in the early 1920s. Shewhart developed the control chart in 1924 and the concept of a state of statistical control. Edwards Deming invited Shewhart to speak at the Graduate School of the U. Deming was an important architect of the quality control short courses that trained American industry in the new techniques during WWII.
Shewhart read the new statistical theories coming out of Britain, especially the work of William Sealy Gosset, Karl Pearson, and Ronald Fisher. The notion that SPC is a useful tool when applied to non-repetitive, knowledge-intensive processes such as research and development or systems engineering has encountered skepticism and remains controversial. In his seminal article No Silver Bullet, Fred Brooks points out that the complexity, conformance requirements, changeability, and invisibility of software results in inherent and essential variation that cannot be removed. In manufacturing, quality is defined as conformance to specification. However, no two products or characteristics are ever exactly the same, because any process contains many sources of variability.
In mass-manufacturing, traditionally, the quality of a finished article is ensured by post-manufacturing inspection of the product. Common Causes » – sometimes referred to as nonassignable, normal sources of variation. It refers to many sources of variation that consistently acts on process. These types of causes produce a stable and repeatable distribution over time.