September 6, 2026 · 8 min read
TL;DR: Quality assurance audits the process, quality control inspects the deliverable. The cost of quality splits into prevention, appraisal, and failure costs, and the exam tests whether you can tell which one a scenario is describing. On a control chart, points inside the limits are ordinary variation, but a run of seven on one side of the mean is a signal to hunt for an assignable cause.
Quality questions look easy right up until the point where two of the four options are both defensible project management. The exam is rarely asking whether you would inspect the work. It is asking whether the scenario describes the process or the product, and whether the money in question was spent before the defect or after it.
One looks at how the work is being done. The other looks at what came out.
Take a rainwater-harvesting design project. Stakeholders want confidence that the processes being followed will produce a product that meets their needs, and the project manager is also asked to find opportunities to improve those processes. That is quality assurance, carried out through process analysis, which examines problems, constraints, and non-value-adding steps inside a process. Nothing in that scenario inspects a deliverable.
Change one word and the answer moves. If the stakeholders wanted confidence that a specific delivered design meets the acceptance criteria, that is quality control, and the technique is inspection.
| Activity | What it examines | Typical trigger words | Output |
|---|---|---|---|
| Quality assurance (PMBOK 8: Manage Quality Assurance, under Governance) | The process producing the work | process, confidence, improvement, audit | Improvement recommendations, change requests |
| Quality control (inspection, which PMBOK 8 places inside Validate Scope) | The deliverable itself | inspect, defect, acceptance criteria, measurement | Verified deliverables, quality measurements |
| Formal acceptance (the other half of Validate Scope) | The customer's sign-off | sign-off, formal acceptance, customer accepts | Accepted deliverables |
Older material lists Control Quality as a process of its own. PMBOK 8 no longer does: inspection now sits inside Validate Scope, which both checks that the quality standards were met and formalises acceptance. The exam still keeps the two questions apart, and that is why acceptance sits in the table as the third option offered when a question wants you to conflate them. Quality control asks "is this correct?" Acceptance asks "will you accept it?" A deliverable can pass the first and fail the second.
Common trap: treating a third-party quality audit as an inspection of the work. When a customer's audit team arrives during execution, what the contractor needs ready is its quality documentation, not its test data. An audit checks whether the agreed policies, procedures, and standards are actually being followed. Work results might get referenced along the way, but the subject of the audit is the quality system. In this bank's 101 quality questions, "the completed work results" is one of the most consistently chosen wrong answers on audit scenarios, and it fails for exactly this reason.
Three categories, and the split is about timing relative to the defect.
Prevention costs come first, spent so the defect never happens: training, tooling, better requirements, design review. Appraisal costs come next, spent finding out whether it happened: testing, inspection, audits. Failure costs come last, and they split again into internal failure (you found it) and external failure (the customer found it). External failure is the expensive corner of the model, because it carries rework plus warranty plus reputation.
Worked example. A component can be redesigned for 40,000 to eliminate a class of defect, or inspected for 15,000 per production run. Two runs are planned. Inspection catches about 80 percent, and each escaped defect costs roughly 200,000 in field replacement, with an expected two escapes across both runs at the current defect rate.
The exam will not usually make you do that arithmetic, but it will ask which category a spend belongs to and which one is cheapest per defect avoided. Prevention over inspection is the standing principle, and the reason is the number in the second line, not a preference for planning.
Note the vocabulary trap in the categories themselves. "Cost of good quality and cost of poor quality" is real language and it means conformance versus nonconformance, but it is the layer above the three categories rather than the categories themselves. When a question asks for the cost categories, three is the answer.
They answer different questions, and the exam picks whichever one the scenario has not prepared you for.
A control chart describes what a process does when nothing unusual is happening. Points inside the control limits are ordinary variation and should be left alone; reacting to them makes the process worse, not better. What matters is the pattern. Nine consecutive points on the same side of the mean is a run, and a run is different evidence from a single outlier. With a stable process each point is roughly equally likely to land above or below the mean, so a long one-sided run is very unlikely by chance. That is the rule of seven, and the response is to identify the assignable cause.
A check sheet does something much simpler. It tallies how often defects occur and where, so concentration becomes visible. When a code inspection turns up critical errors scattered across a codebase with no obvious pattern, the check sheet is what turns "errors everywhere" into "sixty percent of them are in these two modules." Influence diagrams, decision trees, and process decision program charts all show up as distractors on that question, and all three are decision or risk analysis tools rather than tallies.
The distinction worth carrying into the exam: a control chart tells you whether to act, a check sheet tells you where.
What is the difference between quality assurance and quality control? Assurance examines the process and looks for improvements. Control examines the deliverable against acceptance criteria. The word "process" usually points at assurance; "deliverable" or "inspection" usually points at control.
What are the three cost of quality categories? Prevention, appraisal, and failure costs, with failure splitting into internal and external. Conformance versus nonconformance is the same idea one level coarser and is often offered as a near-miss distractor.
What does the rule of seven mean on a control chart? Seven or more consecutive points on the same side of the mean signals something non-random, even with every point inside the limits. Investigate the assignable cause; do not adjust the limits.
What should you do first when a customer rejects a deliverable at inspection? Document the reasons for non-acceptance, specifically: which criteria failed, on which deliverable, on what evidence. The repair, the change request, and the cost impact are all scoped from that record.
The 101 quality questions in PMP Practice are re-certified against PMBOK 8 and the July 2026 Exam Content Outline, and each wrong answer comes with the reasoning that makes it wrong, explained rather than just marked. Start the free 20-question sample with no card and no signup.
Related: What replaced Process Groups and Knowledge Areas · Change requests and approval authority · Process study guide
Sources: PMI — PMP Examination Content Outline, 2026 (PDF) · PMI — PMBOK Guide standards
What is the difference between quality assurance and quality control?
Quality assurance examines the process that produces the work and looks for ways to improve it. Quality control examines the deliverable itself and checks it against the acceptance criteria. Assurance gives stakeholders confidence that the way of working will yield a conforming product; control finds out whether a specific product conforms. On the exam, the word process usually points at assurance and the word deliverable or inspection usually points at control.
What are the three cost of quality categories?
Prevention costs, spent to keep defects from occurring at all. Appraisal costs, spent assessing and inspecting for conformance. And failure costs, both internal (found before delivery) and external (found by the customer). Conformance versus nonconformance is the same idea one level coarser, and the exam sometimes offers it as a near-miss distractor when it wants the three categories.
What does the rule of seven mean on a control chart?
Seven or more consecutive points falling on the same side of the mean signals that something non-random is happening, even though every point is still inside the control limits. A stable process should scatter its points roughly evenly above and below the mean, so a long run on one side is very unlikely by chance. The response is to investigate the assignable cause, not to adjust the limits.
What should you do first when a customer rejects a deliverable at inspection?
Document the reasons for non-acceptance: which acceptance criteria were not met, on which deliverable, on what evidence. Everything downstream runs off that record. The defect repair is scoped from it, any change request is justified by it, and if the disagreement escalates it is the contemporaneous account of what was actually found.