Quality Management
Planning quality
Quality means conforming to defined requirements, not delivering the best possible product. Quality planning defines the standards to be applied, the acceptance criteria for each deliverable (measurable and testable), the reviews, tests and inspections to be performed, and the responsibilities - recorded in a quality plan and quality register. Understand grade versus quality: a low-grade product can still meet its requirements and be fit for purpose.
Assurance versus control
This is the most heavily examined distinction. Quality assurance is process-focused and preventive: are we using the right methods, standards and reviews? It is carried out through audits, process reviews and maturity checks, ideally independent of the team. Quality control is product-focused and detective: inspection, testing, peer review and acceptance of deliverables against criteria. QA asks whether we are doing things right; QC asks whether what we produced is right.
Cost of quality
Classify spend as prevention (training, standards), appraisal (testing, reviews), internal failure (rework before handover) and external failure (defects found by the customer, warranty, reputational cost). Prevention and appraisal are cheaper than failure; external failure is the most expensive.
Traps
Swapping QA and QC; confusing quality with grade or with luxury; assuming gold-plating is good - it is uncontrolled scope; accepting criteria such as 'user friendly' that cannot be tested.
Rule of thumb
Use the PDCA cycle (Plan, Do, Check, Act) as the improvement engine, and never accept a deliverable at a gate without evidence it was reviewed or tested against its written acceptance criteria.