Quality ASSURANCE & Quality control
Quality assurance (QA) and quality control (QC) are two terms that are often used interchangeably. Although similar, there are distinct differences between the two concepts. This page will explain the differences between quality control and quality management, and provide definitions and examples of each.
- Differences between QA and QC
- Industry perspectives on QA and QC
- History of QA and QC
- QA and QC resources
Quality assurance and quality control are two aspects of quality management. While some quality assurance and quality control activities are interrelated, the two are defined differently. Typically, QA activities and responsibilities cover virtually all of the quality system in one fashion or another, while QC is a subset of the QA activities. Also, elements in the quality system might not be specifically covered by QA/QC activities and responsibilities but may involve QA and QC. Figure 1 shows ISO 9000 definitions from ISO 9000:2015: Quality management systems - Fundamentals and Vocabulary.
Quality assurance can be defined as "part of quality management focused on providing confidence that quality requirements will be fulfilled." The confidence provided by quality assurance is
Quality control can be defined as "part of quality management focused on fulfilling quality requirements." While quality assurance relates to how a process is performed or how a product is made, quality control is more the inspection aspect of quality management. An alternate definition is "the operational techniques and activities used to fulfill requirements for quality."
For some service organizations, the concept of quality control may be foreign because there is no tangible product to inspect and control. The quality assurance function in a service organization may not include quality control of the service but may include quality control of any products involved in providing the service.
A service may include products that are documents (such as a report, contract, or design) or tangible products (such as a rental car or units of blood). It may be necessary to control product quality in a service organization to ensure that the service meets customer requirements.
QA, QC, and Inspection
Inspection is the process of measuring, examining, and testing to gauge one or more characteristics of a product or service and the comparison of these with specified requirements to determine conformity. Products, processes, and various other results can be inspected to make sure that the object coming off a production line, or the service being provided, is correct and meets specifications.
Quality Assurance and Audit Functions
Auditing is part of the quality assurance function. It is important to ensure quality because it is used to compare actual conditions with requirements and to report those results to management.
In The Quality Audit: A Management Evaluation Tool (McGraw-Hill, 1988), Charles Mill wrote that auditing and inspection are not interchangeable: “The auditor may use inspection techniques as an evaluation tool, but the audit should not be involved in carrying out any verification activities leading to the actual acceptance or rejection of a product or service. An audit should be involved with the evaluation of the process and controls covering the production and verification activities.”
Formal management systems have evolved to direct and control organizations. There are quality management systems (QMSs) as well as environmental or other management systems, and each of these systems may be audited.
Quality has been defined as fitness for use, conformance to requirements, and the pursuit of excellence. Even though the concept of quality has existed from early times, the study and definition of quality have been given prominence only in the last century.
1920s: Quality Control
Following the Industrial Revolution and the rise of mass production, it became important to better define and control the quality of products. Originally, the goal of quality was to ensure that engineering requirements were met in final products. Later, as manufacturing processes became more complex, quality developed into a discipline for controlling process variation as a means of producing quality products.
1950s: Quality Assurance and Auditing
The quality profession expanded to include the quality assurance and quality audit functions. The drivers of independent verification of quality were primarily industries in which public health and safety were paramount.
Rethinking Statistics For Quality Control (Quality Engineer) As methods used for statistical process control become more sophisticated, it becomes apparent that the required tools have not been included in courses that teach statistics in quality control. A basic description of these tools and their applications is provided.
A Discussion Of The Software Quality Assurance Role (Software Quality Professional) The inability to identify who are actually customers limits the ability of software quality assurance engineers in the performance of their duties. Correcting this oversight enables the SQA engineer to provide greater value to customers by assuming the role of auditor as well as that of software and systems engineer.
From The ASQ Certified Quality Auditor Handbook, ASQ Quality Press.