Quality Control and Quality Assurance

You have heard the terms before, but do you really know the difference between quality control and quality assurance?

  • Quality control (QC) refers to the activities associated with the validating the quality of deliverables. Quality control is also called “inspection” since it means that the quality is validated in a deliverable (or draft deliverable) that already exists. QC is used to verify that deliverables are of acceptable quality and that they meet the completeness and correctness criteria established in the quality planning process. Quality control is conducted continually throughout a project and is the responsibility of team members and the project manager.
  • Quality assurance (QA) does not refer directly to the specific deliverables themselves. It refers to the process used to create the deliverables. Quality assurance is also referred to as “prevention”. Quality assurance activities focus on the processes used to manage and deliver the solution, and can be performed by a manager, client or a third-party reviewer. For instance, an independent project reviewer might not be able to tell if the content of a specific deliverable is acceptable. However, he should be able to tell if the deliverable seems acceptable based on the process used to create it. He can determine, for instance, whether reviews were performed, whether it was tested adequately, whether the client approved the work, etc.

Quality assurance is performed at a higher level than quality control. For example, you might inspect 100% of the product that you are manufacturing. This physical inspection is an example of quality control. During your inspections you discover that 3% of your products are faulty and need to be destroyed. You consider this an acceptable expense and continue this way – always happy to catch the 3% of the product that contains defects and throwing them away.

If you use quality assurance techniques however, you would determine what is causing this 3% defect rate. Once you uncovered the cause for the errors, you would change your manufacturing process to try to eliminate the errors. This work on your processes is quality assurance. Changes made to your process (quality assurance) results in fewer defects found through the inspection process (quality control).


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