Spearman’s rho, as it is sometimes called, is used when the data are ranks rather than raw scores. For example, assume the principal and assistant principal have independently ranked the 15 teachers in their school from first, most effective, to 15th, least effective, and you want to assess how much their ranks agree. You would calculate the Spearman’s rho by putting the paired ranks into the Pearson r formula or by using a formula developed specifically for rho.
Spearman’s rho is interpreted the same as is Pearson r. Like the Pearson product-moment coefficient of correlation, it ranges from –1.00 to +1.00. When each individual has the same rank on both variables, the rho correlation will be +1.00, and when their ranks on one variable are exactly the opposite of their ranks on the other variable, rho will be –1.00. If there is no relationship at all between the rankings, the rank correlation coefficient will be 0. If you have a computer or calculator program for Pearson r, you can calculate Spearman’s rho by putting the ranks into that program.