4.1Measuring What Matters

Metrics are the language of accountability. Without them, QA is a matter of opinion ("I think the product is ready" vs "I don't think it's ready"). With them, QA becomes a discipline grounded in evidence ("The defect escape rate is 4%, below our 5% threshold, and all critical paths have automated coverage"). This section covers the metrics every QA engineer should know, how to calculate them, and which ones actually drive decisions.