What is the Difference between QA and QC? How do They Work?

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Many people and organizations are confused about the difference between Quality Assurance (QA) and Quality Control (QC). These are two different but closely related concepts, and understanding the difference between QA and QC is important for a deeper understanding of quality work.

QA (Quality Assurance)

What does the term “assurance” mean?

More simply put, it is a guarantee or trust that gives confidence.

Quality assurance is a guarantee of the quality of a product. It is a guarantee that the output of a process is free of defects and meets the requirements of the specification.

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Quality assurance is a process-based approach whose main objective is to prevent all kinds of defects that may occur when a product is delivered during the quality planning phase in order to avoid rework or scrap.

Quality assurance is a proactive process. It emphasizes the importance of quality planning, processes, and quality standards.

The quality assurance process becomes involved at the beginning of the project to understand the quality requirements of the product.

Once the product quality requirements are identified, a quality plan is developed to meet those requirements.

Tools used in the quality assurance process

The tools used throughout quality management fall into three categories depending on their purpose: process analysis, process management/control, and quality audits.

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In a quality audit, a group of internal or external audit specialists reviews processes and procedures.

If any discrepancies are found, they provide recommended corrective actions and may also inform us of potential opportunities for improvement (OFI).

Quality audits are an important tool to ensure that process procedures are being followed.

In a process analysis, we analyze the process to identify any opportunities for improvement, discover the root causes of problems that occur and address them, and so on.

And so forth, in a cycle of continuous improvement.

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Process management/control tools, including a variety of graphical tools, can help us find ideas and make judgments, and can also direct our resources to higher priority issues.

Some examples of process management/control tools are affinity diagrams, tree diagrams, network diagrams, etc.

QC (Quality Control)

Quality Assurance (QA) is a process-based approach; Quality Control (QC), on the other hand, is a product-based approach.

Quality control involves quality activities and quality techniques used to meet product quality requirements.

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When we initiate QC, often the project work has already started. Therefore, it is a relatively passive approach used to help us identify defects in the product.

The goal of quality control is to ensure that the product delivered to the customer is free of defects and meets acceptable quality requirements.

If the delivered product is defective, then appropriate corrective actions need to be taken.

Simply put, the quality control process has two objectives: to detect any defects in the product and correct them, and to verify the quality of the product.

Quality assurance and quality control are interdependent.

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The quality control process receives input from the quality assurance process and feeds it back to the quality assurance process for continuous improvement of the quality assurance effort.

For example, if the project team finds a defect during project execution, they will correct the defect and then feed the issue back to the QA team.

The QA staff will investigate the cause of this defect from a process and system perspective, take corrective/preventive action and update the relevant process documentation accordingly.

Once the process has been updated, the quality control personnel will follow the process as defined by the QA team so that the defect does not recur.

Tools used in the quality control process

In general, we use three types of tools in the quality control process. These tools include inspections, statistical sampling, and the seven QC practices.

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In inspection, defects are physically inspected and checked for compliance.

In statistical sampling, a certain number of samples from a lot are selected and checked for defects and conformance.

The seven QC techniques are scattered diagram, control chart, bar chart, checklist, Pareto chart, cause and effect analysis, and flow chart. These tools can help us to find defects and confirm the consistency of the product.

The difference between quality assurance and quality control

1. Quality assurance focuses on preventing defects, while quality control focuses on identifying defects.

2. Quality assurance works to effectively avoid any anticipated defects. Quality control is the attempt to find defects and correct them.

3. Quality assurance is an active process and quality control is a passive process.

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4. Quality assurance is a process-based approach, while quality control is a product-based approach.

5. Quality assurance includes process quality management, while quality control is used to verify the quality of the product.

In general, quality assurance and quality control are closely related and have the same goal of providing a defect-free product.


The goal of both quality assurance and quality control is to make products free of defects and to ensure that they meet requirements.

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In terms of objectives, quality assurance and quality control are the same, but the difference lies in the approach, with quality assurance being a process-based approach and quality control being a product-based approach.

Quality assurance plans the product realization process so that the products produced through this process are free of defects, while quality control is responsible for checking the products to ensure that they enter the market without defects.

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