Type or paste a DOI name into the text box. Further documentation is available here. ISO 9000 defines as “part of quality management focused on providing confidence that quality requirements will be fulfilled”. This defect prevention in quality assurance differs subtly from information technology auditing and assurance james hall pdf free download detection and rejection in quality control, and has been referred to as a shift left as it focuses on quality earlier in the process.
The terms “quality assurance” and “quality control” are often used interchangeably to refer to ways of ensuring the quality of a service or product. For instance, the term “assurance” is often used as follows: Implementation of inspection and structured testing as a measure of quality assurance in a television set software project at Philips Semiconductors is described.
The term “control”, however, is used to describe the fifth phase of the DMAIC model. DMAIC is a data-driven quality strategy used to improve processes. Quality assurance comprises administrative and procedural activities implemented in a quality system so that requirements and goals for a product, service or activity will be fulfilled.
It is the systematic measurement, comparison with a standard, monitoring of processes and an associated feedback loop that confers error prevention. This can be contrasted with quality control, which is focused on process output.
QA includes management of the quality of raw materials, assemblies, products and components, services related to production, and management, production and inspection processes. The task of engineering is to make it work once, while the task of quality assurance is to make it work all the time. Historically, defining what suitable product or service quality means has been a more difficult process, determined in many ways, from the subjective user-based approach that contains “the different weights that individuals normally attach to quality characteristics,” to the value-based approach which finds consumers linking quality to price and making overall conclusions of quality based on such a relationship. During the Middle Ages, guilds adopted responsibility for the quality of goods and services offered by their members, setting and maintaining certain standards for guild membership.
Royal governments purchasing material were interested in quality control as customers. For this reason, King John of England appointed William de Wrotham to report about the construction and repair of ships. Centuries later, Samuel Pepys, Secretary to the British Admiralty, appointed multiple such overseers to standardize sea rations and naval training. Prior to the extensive division of labor and mechanization resulting from the Industrial Revolution, it was possible for workers to control the quality of their own products.
The Industrial Revolution led to a system in which large groups of people performing a specialized type of work were grouped together under the supervision of a foreman who was appointed to control the quality of work manufactured. During the time of the First World War, manufacturing processes typically became more complex, with larger numbers of workers being supervised. This period saw the widespread introduction of mass production and piece work, which created problems as workmen could now earn more money by the production of extra products, which in turn occasionally led to poor quality workmanship being passed on to the assembly lines. Pioneers such as Frederick Winslow Taylor and Henry Ford recognized the limitations of the methods being used in mass production at the time and the subsequent varying quality of output.
Shewhart at Bell Laboratories in the early 1920s. Shewhart developed the control chart in 1924 and the concept of a state of statistical control.
Statistical control is equivalent to the concept of exchangeability developed by logician William Ernest Johnson also in 1924 in his book Logic, Part III: The Logical Foundations of Science. T that included Harold Dodge and Harry Romig, he worked to put sampling inspection on a rational statistical basis as well.