virhetiheys

Virhetiheys is a Finnish term that translates as error density or defect density. It denotes the number of detected faults, errors or defects in a product or process normalized by a size measure, and is used as a quantitative indicator of quality or reliability. In software engineering virhetiheys is commonly expressed as defects per thousand lines of code (defects/KLOC) or per function point; in manufacturing it may be defects per million opportunities or per unit produced.

Purpose and use: virhetiheys supports benchmarking, trend analysis and risk assessment by enabling comparisons across modules, releases, suppliers or production batches. It is used to prioritize testing and inspection effort, to evaluate the effect of process changes, and in contractual or regulatory contexts where quality metrics are required.

Limitations: the metric depends on how defects are defined, detected and recorded, and on choice of size normalization. Differences in testing rigor, severity thresholds, defect classification and code granularity can make comparisons misleading. Low virhetiheys does not guarantee absence of critical defects; high values may reflect more intensive detection rather than poorer quality.

Best practices: accompany virhetiheys with contextual data (severity breakdown, detection phase, test coverage), use consistent counting rules, and combine it with complementary measures such as failure rate, mean time to failure and customer-reported defects. Interpreted carefully, virhetiheys is a useful but imperfect indicator for managing quality and guiding improvement efforts.