These terms are very closely related to each other. This is the reason why most of the time PMP aspirants have trouble understanding the difference between these two terms.
Let us first understand the concept of Quality.
Philip Crosby popularized the concept of the cost of poor quality and advocated “zero defects” and “Prevention over inspection”. He believed that quality is “conformance to requirements”
So the idea behind these concepts is that everything we produce should be error free from the start, because it’s more costly to fix an error afterwards.
So… how can we assure that our deliverables are produced error free?
We have to put appropriate processes in place; processes that are aimed at helping us produce these deliverables without errors every time. But because there will always be some deviation from even the best processes, we also have to put some controls in place, which measure the results after the fact, so that we can make adjustments if necessary.
Quality Assurance therefore encompasses the processes that are aimed at preventing any defects and Quality Control are the measurements we have in place to detect and repair any remaining defects.
PMBOK® Guide Fifth Edition defines Quality Assurance processes as
“The process of auditing the quality requirements and the results from quality control measurements to ensure appropriate quality standards and operational definitions are used.”
PMBOK® Guide Fifth Edition defines Control Quality processes as
“The process of monitoring and recording results of executing the quality activities to assess performance and recommend necessary changes.”
So let’s assume that you are manufacturing a new product.
In Quality Assurance you put all the processes in place to ensure that product is manufactured defect free. This would include the types of manufacturing equipment used, training people and documenting all production processes.
Quality Control on the other hand comes into play only after the fact, by testing the finished product. For instance you do a sample testing to see if a randomly picked product from your production line passes or fails the standards.
Differences between Quality Assurance and Quality Control
• Quality Assurance is process oriented and focuses on defect prevention; while Quality Control is product oriented and focuses on defect detection.
• Quality Assurance makes sure you are doing the right things, the right way; Quality Control makes sure the results of what you’ve done are what you expected.
• Quality Assurance is an Executing Process Group process, so it gets executed when we are executing the project management plan; Quality Control is an Monitoring and Controlling Process Group process, so it uses the deliverables and data generated by executing process groups and compare them against the project management plan.
• Quality Assurance helps in building quality in the product; Quality Control helps in detecting defects left by executing a process so they do not reach to customers.
• Quality Assurance is our first line of defense against producing non compliant product; Quality Control is our second line of defense which checks the product to verify is it good to deliver to the customer.
• Quality Assurance uses tools like Auditing to check how the team is complying the quality management plan; Quality Control uses inspection as a tool to check how the output of executing process (deliverable) is adhering to the project management plan.
• Quality Assurance activities are determined before production work begins and these activities are performed while the product is being developed; Quality control activities are performed after the product is developed.
I hope you liked this article.