Explain like I'm five · SW Eng

What are QA and QC?

Watching that the editing process is followed, and reading the finished manuscript to mark it up, are two different jobs.

there's a typo on page 12!that book is already printed and in readers' hands

A reader found a typo — after everything was already printed.The book is already in readers' hands, so the typo is hard to undo.

already printedthe later a flaw is found, the more it costs to fixfixing it after printing means reprinting everything

Found after printing, a typo costs far more to fix than at the manuscript stage.Fixing it after printing means reprinting everything.

QA: process checkproofing steps followed?QA checks the way it's made, QC checks what came out of itboth are needed to catch typos before they reach readers

QA checks how it's made; QC checks what came out of it.Both are needed to catch typos before they reach readers.

QA = process checkwatches the proofing procedure itself
QA = prevention-focusedfixes the process so fewer typos appear
QC = product inspectionreads the finished manuscript directly
QC = find and mark flawsmarks each one with a red pen
QA (quality assurance)was the process followed?org standard kept?prevention-focusedQC (quality control)inspect the finished manuscriptmark the typosoutput-focusedQA looks at the whole editing process early; QC looks at the finished manuscript late

QA and QC differ in scope and timing.QA looks at the whole editing process early; QC looks at the finished manuscript late.

QC alone, no QA: flaws are found late and cost morewith QA, fewer flaws appear in the first placeQC is the net that catches flaws, QA is the care that makes fewer in the first place

QA and QC are both needed, but they play different roles.QC is the net that catches flaws; QA is the care that prevents them in the first place.

In one breath

QA checks whether the process followed the standard; QC inspects the finished product itself to find defects.

QA (Quality Assurance) checks adherence to process standards to prevent defects from happening; QC (Quality Control) directly inspects and tests the product to find defects that did happen. QA leans toward prevention, QC toward detection — they complement rather than replace each other.

When grown-ups say it

Quality Assurance
Checking whether the editing process was followed. Closer to prevention.
Quality Control
Directly inspecting the finished manuscript. Closer to detection.
Verification
Checking "did we build it right." Compares each stage's output against its spec.
Validation
Checking "did we build the right thing." Checks the result against what users need.
Defect
A typo left in the manuscript. What QC directly hunts for.
ISO 9001
An international standard for quality management systems. One external standard QA can follow.
IS Audit/PMO
Checking quality and schedule across many books at once. Looks at an even wider scope than QA. → the checker who watches the whole publishing run
CMMI
How mature an organization's working processes are. QA is one of the practices CMMI looks at.
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