The C in QC gives you the clue: it is about controlling quality. QC is about inspections, checks and tests.
QC is used to distinguish between what is ‘good’ (OK, passes, meets requirements, conforms, whatever you want to call it) and what is ‘bad’ (not OK, fails the test, doesn’t conform, nonconformity, nonconforming product or service, doesn’t meet requirements).
The focus of QC is to verify the quality of the output: of the service or product delivered to a customer, but often also involves tests, checks, measurements or other activities on parts or components or important stages before the service/product reaches ‘final’ status.
Examples of QC for services
- Lead architect reviews another architect’s work before it is submitted to the client for review and discussion.
- Peer review of a psychologist’s counselling approach and notes for a client
- Editorial review of written work for grammar, spelling, inconsistencies and so forth, before it is published.
- Restaurant chef ‘at the pass’ inspecting dishes before they are taken out to be served to customers.
Examples of QC on product
- Inspection of final product before delivery to customer
- Inspection of parts in the process of manufacturing (e.g., ‘first off’ to check that a CAD/CAM program is working correctly before doing a full production run)
- Tests of modules of an IT system; tests of the whole IT system
- Measurement of a component, and comparison of the actual dimensions measured to those shown on the engineering drawing.
The A in QA stands for Assurance. It is about assuring quality (yes, really).
QA involves thinking about what is required to ensure quality will be achieved, and to set out processes, standards, procedures and/or policies to do that. Typical results of QA are quality plans, inspection, and test plans (ITPs), documentation and training. It moves a step up from finding the failures to aiming to prevent or eliminate them.
The focus of QA is to provide confidence that requirements and standards are met, and that processes and system have been followed.
Examples of QA
- A checklist for assembly of product (the procedure/process as a series of steps that must be done)
- A set of recipes used in a restaurant, with pictures showing how each dish is to be plated up.
- A written procedure
- A set of processes for a product that cover the whole ‘life cycle’ from getting customer requirements, through designing the product, procuring the materials or parts, manufacturing, storage and delivery.
- A set of processes for a service that cover the whole ‘life cycle’ from establishing what the customer requires, through designing the service, developing and delivering it
If the only part of quality you use is QC, you would be constantly checking, measuring and testing your services or widgets, but even when you found some that failed, you wouldn’t ever do anything to your system to improve it, to understand and eradicate problems you find when inspecting, testing or measuring or attempt to remove those failures.
If you only used QA, you would perhaps have what look like/sound like a great set of processes and paperwork. But you never actually test, check, or measure the product or service to verify that it does what it is supposed to do. (Which does not say a lot for assurance, in my eyes.)
In either case, the service or product is unlikely to meet what your customer wanted and expected.