Difference Between QA and QC

Many people and organizations are confused about the difference between quality assurance (QA), quality control (QC), and testing. They are closely related, but they are different concepts. Since all three are necessary to effectively manage the risks of developing and maintaining software, it is important for software managers to understand the differences.

They are defined below:

• Quality Assurance: A set of activities designed to ensure that the development and/or maintenance process is adequate to ensure a system will meet its objectives. The planned and systematic activities implemented in a quality system so that quality requirements for a product or service will be fulfilled.


• Quality Control: A set of activities designed to evaluate a developed work product. The observation techniques and activities used to fulfill requirements for quality.


• Testing: The process of executing a system with the intent of finding defects. (Note that the "process of executing a system" includes test planning prior to the execution of the test cases.)

QA activities ensure that the process is defined and appropriate. Methodology and standards development are examples of QA activities. A QA review would focus on the process elements of a project - e.g., are requirements being defined at the proper level of detail. In contrast, QC activities focus on finding defects in specific deliverables - e.g., are the defined requirements the right requirements. Testing is one example of a QC activity, but there are others such as inspections. Both QA and QC activities are generally required for successful software development.

Controversy can arise around who should be responsible for QA and QC activities -- i.e., whether a group external to the project management structure should have responsibility for either QA or QC. The correct answer will vary depending on the situation, but general experience suggests that:

• While line management should have the primary responsibility for implementing the appropriate QA, QC and testing activities on a project, an external QA function can provide valuable expertise and perspective.

• The amount of external QA/QC should be a function of the project risk and the process maturity of an organization. As organizations mature, management and staff will implement the proper QA and QC approaches as a matter of habit. When this happens only minimal external guidance and review are needed.