z-score
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Meaning
A statistical measurement that describes a value's relationship to the mean of a group of values, expressed in terms of standard deviations from the mean.
A standardized value used to compare data points from different normal distributions.
Structure
Usage
A z-score of 2.0 indicates the data point is two standard deviations above the mean.
Researchers converted the test results into z-scores to compare performance across different age groups.
An outlier was identified because it had a z-score with an absolute value greater than 3.
Etymology
The term is a modern compound from the field of statistics, formed in the 20th century. The letter 'z' was adopted as a standard notation by statisticians, following the convention of using letters like 'x' and 'y' for variables, to specifically denote a data point that has been standardized. The word 'score' originates from Old English 'scoru,' meaning a notch or tally for keeping count, which evolved through Old Norse to mean a record of points. The compound 'z-score' thus logically represents a "standardized numerical value," where 'z' signals the specific statistical transformation and 'score' provides the concept of a measurable quantity.
Analysis
- z: English (Letter). The letter 'z' is used here as a variable symbol, representing a standardized or transformed value in statistical notation. - score: English (Noun). In this context, it means a numerical value or measurement, derived from its general sense of a record of points or marks.