Quality control process

Quality control (Control Quality) is the process of monitoring and recording the results of executing quality activities to assess performance and recommend necessary changes. It determines whether project results meet the quality standards and identifies ways to eliminate the causes of unsatisfactory performance. It is performed throughout the project.

Process

Deliverables -> Inspect / Test -> Compare with standard
       -> Within limits? -- Yes -> Accept (validated deliverables)
                         -- No  -> Find cause -> Corrective action
                                    -> Rework -> Re-inspect

1. Collect data: take measurements of deliverables and processes.
2. Inspect and test against the quality metrics and requirements.
3. Analyse results using statistical tools.
4. Identify defects and their causes.
5. Recommend corrective action, defect repair or preventive action.
6. Rework and retest until accepted.
7. Record results and update documents.

Tools and techniques

• Seven basic quality tools: cause-and-effect (fishbone) diagram, flowchart, check sheet, histogram, Pareto chart, control chart, scatter diagram.
• Statistical sampling.
• Inspection (reviews, walkthroughs, audits).
• Approved change request review.

Outputs

Quality control measurements, validated changes, validated deliverables, work performance information, change requests and updates.

In IT projects

Code reviews, unit/integration/system/acceptance testing, defect tracking and regression tests.

QC concepts

• Prevention versus inspection: keeping errors out of the process is better than finding them later.
• Attribute sampling (pass/fail) versus variable sampling (measured on a continuous scale).
• Tolerances and control limits.
• Special causes versus random (common) causes.

Example: After each sprint, testers run test cases on a new module; a defect log is prepared and the defects are fixed before the demo.