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12 March 2013

Difference between Quality Assurance and Quality Control

Major Differences between QA and QC

The difference between Quality Assurance (QA) and Quality Control (QC) can easily get lost among all the words. Some simple contrasts will help separate the two in your mind.
1. QA is primarily proactive. QC is primarily reactive.
2. QA focuses on the methods. QC focuses on the results.
3. QA uses some statistical methods to analyze how work is done, but QC uses a lot of measurements and statistics to make sure you get the right results.
4. QA's scope how the project gets done, whereas QC's scope includes how well the work got done and how well the product or service meet the requirements.
Putting those together, Quality Assurance assures you will get the product or service right by making sure the work gets done using the best methods. Quality Control measures and analyzes to control the quality of the product, service, or project execution, and to verify whether it meets the requirements.
If you view your studies of QA and QC with this framework in mind, the rest of the differences will make a lot more sense.
I like food, so let's use a restaurant as an example.  Normally a restaurant would be Operations (not Project), so let's assume that our fine establishment will cater an event and, therefore, Chef Boyardee has a project to manage.

QA (proActive Execution) may find weaknesses in processes or standards due to problems that have occurred. For example, Waiter A wanted to take a break, but Waiter B did not know to whom to deliver the food. We have identified a new stakeholder requirement: Waiters need the ability to hand off orders to each other.

The head waiter improves the process by requiring all waiters to include the table number and seat code for each order. Thus, QA reacts to the problem, focuses on the processes and tools, and enables improvements to the project.

QC (reactive Control) may find a trend indicating an approaching problem. The Chef inspects the food before it is served and notices less steam rising from the tandoori vegetables. Although the food is still acceptable, the temperatures are trending downward.

Before customers start receiving food below the Lower Control Limit of temperature, the Chef determines that the tandoori cook's burners are not getting enough propane. The Chef alerts the cook, who swaps in a fresh propane tank.

Thus, QC Monitored the product, analyzed the data, performed a Root Cause Analysis, and enabled proactive control of an issue before it became a problem.
Warnings about Generalizations
Remember, "proactive" and "reactive" are generalization to differentiate the two processes. QA (proActive Execution) can be reactive and QC (reactive Control) can be proactive, as well.
Is it safe to say that QA involves polices and procedures ... while QC involves actual work on a product or service?
Yes, as a generalization, it is "safe to say that QA involves polices and procedures ... while QC involves actual work on product or service."
One important note: Process and procedure are ambiguous terms, and every organization has its own definitions of them. Both QA and QC can initiate improvements to (processes or procedures).
For example, one level of (process or procedure) might instruct personnel to collect the materials and drawings, then have the machinist construct the widget, then have QC inspect it.
Another level of (process or procedure) might instruct the machinist how to program the machine, mount the raw materials, push the buttons, release and label the widget, dispose the scrap, and prepare the machine for the next task.
From that point of view, QA might perform quality audits to verify that a high level (process or procedure) is being followed, but QC might verify that a detail-level (process or procedure) was followed correctly and with the right results. Both QA and QC involve (processes or procedures).
Reminder:  This discussion is just about the major differences. When you look at the details and the ambiguous terms makes it confusing, refer back to the big picture for perspective.

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