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In statistics, Spearman's rank correlation coefficient or Spearman's ρ, named after Charles Spearman [1] and often denoted by the Greek letter (rho) or as , is a nonparametric measure of rank correlation (statistical dependence between the rankings of two variables).
Spearman tested how well people performed on various tasks relating to intelligence. Such tasks include: distinguishing pitch, perceiving weight and colors, directions, and mathematics. [2] When analyzing the data he collected, Spearman noted that those that did well in one area also scored higher in other areas.
Pearson/Spearman correlation coefficients between X and Y are shown when the two variables' ranges are unrestricted, and when the range of X is restricted to the interval (0,1). Most correlation measures are sensitive to the manner in which X and Y are sampled. Dependencies tend to be stronger if viewed over a wider range of values.
A rank correlation coefficient measures the degree of similarity between two rankings, and can be used to assess the significance of the relation between them. For example, two common nonparametric methods of significance that use rank correlation are the Mann–Whitney U test and the Wilcoxon signed-rank test .
It comprises 60 multiple choice questions, listed in order of increasing difficulty. [2] This format is designed to measure the test taker's reasoning ability, the eductive ("meaning-making") component of Spearman's g (g is often referred to as general intelligence). The tests were originally developed by John C. Raven in 1936. [3]
Charles Edward Spearman, FRS [1] [3] (10 September 1863 – 17 September 1945) was an English psychologist known for work in statistics, as a pioneer of factor analysis, and for Spearman's rank correlation coefficient.
The Spearman–Brown prediction formula, also known as the Spearman–Brown prophecy formula, is a formula relating psychometric reliability to test length and used by psychometricians to predict the reliability of a test after changing the test length. [1] The method was published independently by Spearman (1910) and Brown (1910). [2] [3]
Charles Spearman developed in 1904 a procedure for correcting correlations for regression dilution, [10] i.e., to "rid a correlation coefficient from the weakening effect of measurement error". [11] In measurement and statistics, the procedure is also called correlation disattenuation or the disattenuation of correlation. [12]