Spearman rank difference correlation coefficient (Spearman’s RHO) - American Education
A mathematical method of relating two different sets of rankings—I.Q. rankings and rankings on a reading test, for example—for the same group of individuals. Using a complex formula, a teacher can determine whether student rankings on a particular test have a direct, inverse or no relationship with rankings on another test. Thus, a reading test whose student rankings are the reverse of their intelligence-test rankings may have little merit as a measure of reading skills. Rank correlations range from –1.00 to +1.00, with the former indicating an inverse correlation, 0.00 indicating no correlation and +1.00 a perfect correlation.