13 October 2011

Difference between QA and QC

As we've talked in a previous post about the Definition of Quality, with these 2 terms exist the same “issue” where every single person/organization defines Quality Assurance (QA) and Quality Control (QC) in a bit different way. Also, many people including HHRR (Human Resources) and quality professionals do not know what QA and QC really means, and what the difference is between both terms. For those reasons, these concepts are often used interchangeably, and in some organizations one department performs the activities of both.

The truth is that both terms have strong interdependence; QA relies mostly on the QC feedback and both work to deliver good quality products/services; but they are different processes.

Next table shows the differences between them.

Definition from ASQ.org
Assurance: The act of giving confidence, the state of being certain or the act of making certain.

QA: The planned and systematic activities implemented in a quality system so that quality requirements for a product or service will be fulfilled.

Other definition

QA is a failure prevention system that predicts almost everything about product safety, quality standards and legality that could possibly go wrong, and then takes steps to control and prevent flawed products or services from reaching the advanced stages of the supply chain.

Definition from ASQ.org
Control: An evaluation to indicate needed corrective responses; the act of guiding a process in which variability is attributable to a constant system of chance causes.

QC: The observation techniques and activities used to fulfill requirements for quality.

Other definition

QC is a failure detection system that uses a testing technique to identify errors or flaws in products and tests the end products at specified intervals, to ensure that the products or services meet the requirements as defined during the earlier process for QA.

QA department develops all the planning processes and procedures in order to try to make sure that the products manufactured or the service delivered by the organization will be of good quality.

As some process parameters cannot be controlled, QC department checks the products or services for defects that happen due to these parameters, trying to achieve the overall QC objective of providing a defect-free product or service to the customers.

QA defines the standards/methodology to be followed in order to meet the customer requirements. *

QC ensures that the defined standards are followed at every step.*

* This is done by conducting various tests and checks. Based on them, the QC prepares regular reports that act as an input to the QA department which then reviews the same and decides on the corrective and preventive actions required in the processes.

In general, the QA activities are done before the product is manufactured or the service delivered (proactive approach).

The QC activities are done during the manufacturing process and once the product is manufactured.

QA is process oriented.

QC is product oriented.

QA makes sure you are doing the right things, the right way.

QC makes sure the results of what you've done are what you expected.

QA tasks are conducted by managers, third party auditors, and customers. *

QC tasks are executed by experts who are directly involved with the design, or manufacture of a product on the shop floor such as engineers, inspectors, etc. *

For this reason, one person cannot perform both activities (QA and QC) because will result in a conflict of interest.

- A QA audit would focus on the process elements of a project. e.g.: Are requirements being defined at the proper level of detail?
- Process documentation
- Establishing standards
- Developing checklists
- Conducting internal audits

- A QC review will focus on product elements. e.g.: Are the defined requirements the right requirements?
- Performing inspections
- Preforming testing
- QC detected a recurrent problem with the quality of the products. QC provides feedback to QA personnel that there is a problem in the process or system that is causing product quality problems. QA determines the root cause of the problem and then brings changes to the process to ensure that there are no quality issues in future.

NOTE 1: Quality Assurance AKA Quality Guarantee

NOTE 2: QA/QC are not limited to the manufacturing field, they can be applied to any business or non-business activity such us services, software, banking, transportation, office, education, etc.

Both departments are essential to maintain good quality of the deliverables.
And keep in mind no matter how you define QA and QC,  the goal is: to delivery good quality.

1. QA and QC activities performed by the same person. Read question
2. QA and QC personnel report to the same manager. Read question 

If you are a member of the ASQ group in LinkedIn, you can read more about this topic by clicking here.

So, how do you define QA and QC?


  1. I really appreciate the word done by you. Excellent post.

  2. This is an excellent table that I would encourage those who need to train others in Quality Assurance (and QC) to use. Thank you for sharing it!

  3. Excelente. Te seguiremos Jimena.

    El equipo de ofinext.

  4. Thanks everyone for the messages; I really appreciate you stop by and let me know your thoughts. Gracias!

  5. Very nice post

  6. Thank you so much for this article, Jimena. It can be difficult to keep everything straight and this cleared it up wonderfully. Great post!

    1. Thanks Vivienne! Glad it helps.

      Keep in contact!

  7. Thank you very much for this wonderful comparison. After reading a dozen of comparisons on the net , I landed up here and simply it has the best.
    keep it up.

  8. It’s a very useful & qualitative information shared on Software assurance & Quality control.
    Indeed a great share.

  9. I would like to say that this blog really convinced me to do it! Thanks, very good post.
    HR Outsourcing

  10. Wow, it couldn't be better than this

  11. well done. goo job.


    Mohamed Haja. S


  12. That was really helpful my job has me doing both jobs calling it a Quality Technical Specialist.