Quality Control

Quality control is often confused with quality assurance, but they serve different purposes. Quality assurance (QA) is proactive and process-focused: designing systems and procedures to prevent defects. Quality control is reactive and product-focused: inspecting and testing to catch defects before they reach customers. Both are necessary for a robust quality management system. QC activities vary by industry and product complexity. In food manufacturing, QC might involve temperature checks, microbial testing, and visual inspection. In electronics, it might include functional testing, burn-in testing, and X-ray inspection of solder joints. In pharmaceuticals, it involves extensive chemical analysis and stability testing. The level of inspection can range from 100% inspection of every unit to statistical sampling where a representative sample determines whether the entire lot passes or fails. Statistical quality control, pioneered by Walter Shewhart and W. Edwards Deming, uses control charts to monitor process variation. When measurements fall outside control limits, the process is considered "out of control" and production is halted for investigation. This approach catches problems during production rather than after, reducing scrap and rework. Non-conformance management is a critical QC function. When defects are found, they must be documented, investigated for root cause, and corrected. A good quality management system tracks non-conformances by type, source, and frequency to identify systemic issues rather than treating each incident in isolation.