Poikkeama

Poikkeama is a Finnish noun meaning deviation or discrepancy: the difference between something observed and a reference value, target, or standard. The word derives from the verb poiketa, to deviate.

In mathematics and statistics, poikkeama refers to the difference between an observed value x_i and a reference value a. A signed deviation is x_i − a; an absolute deviation is |x_i − a|. Deviations from the mean are used in many statistical measures, and the term is used in practical contexts alongside virhe (error) and hajonta (variance). The standard deviation is called keskihajonta in Finnish.

In quality control and engineering, poikkeama denotes a measurement or product that falls outside prescribed specifications or tolerances, i.e., a deviation from required values. Such poikkeamat are investigated to identify root causes and to correct processes. The term is common in audit reports and nonconformity tracking.

In meteorology and climatology, poikkeama describes the difference between observed values and forecasts or baselines, such as temperature poikkeama from normal values. It can refer to outliers, but more often indicates a deviation from expectation.

Etymology and terminology: poikkeama originates from poiketa, underscoring departure from a reference point. Related concepts in Finnish include poikkeavuus (deviation/anomaly), hajonta (variance), and keskihajonta (standard deviation), with poikkeama emphasizing departure from a standard rather than random error alone.