correlation
Pluralcorrelations
- 1A reciprocal, parallel, or complementary relationship between two or more comparable things, where changes in one correspond to changes in another.
Like the way the tide rises and falls in step with the phases of the moon.
Researchers noted a striking correlation between rising temperatures and crop failure.
The correlation between the two datasets surprised the analysts.
Similarrelationship, connection, link, association, correspondence
Note
Middle French corrélation reached English and was reshaped as correlate plus -ion, so the noun names the condition of things that correlate. It is usually graded by an adjective: a clear, strong, weak or positive correlation. Strong and weak describe how closely the things match, while positive and weak point toward the statistical measure, where those words carry exact values.
- 2In statistics, any of several measures of how strongly, and in which direction, two random variables are linearly related.
Analysts reported a correlation of 0.85 between the two stock indices.
A weak correlation between the variables suggested little predictive value.
Note
Statistics turns the everyday relationship into a number. The most common version is the Pearson coefficient, which runs from −1 for a perfect inverse relationship, through 0 for none, to +1 for a perfect direct one. The sign gives the direction and the size gives the strength. In reporting the noun is freely countable and takes between: bigger correlations between mental health and time of year.
- 3In projective geometry, an isomorphism between a projective space and the dual of a projective space, often its own dual.
A correlation maps each point of the projective plane to a line in the dual plane.
Composing a correlation with itself yields a projective collineation.
Note
Projective geometry's correlation has nothing to do with data. It is a map that reverses incidence, sending points to hyperplanes and hyperplanes back to points. In the plane, that means points to lines. Its counterpart is the collineation, which keeps points as points. A correlation that is its own inverse earns a name of its own, a polarity.
Practice
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Origin
Borrowed from Middle French corrélation, and analyzable as 'correlate' plus the suffix '-ion'.