SPEARMAN RANK COEFFICIENT (RHO)

Charles Spearman, a British psychologist , is given credit for the first work on the relationship between ranks. His early writings on the subject became known as Spearman's rank-order correlation. (In reality it was Galton, not Spearman, who developed the idea of rank order correlation and it was Pearson who derived the formula.) Anyway, The Spearman rank coefficient is referred to as the Spearman rho because it is denoted by the Greek letter p. It is a nonparametric measure for use with data that are either reduced to ranks or collected in the form of ranks.

In testing the significance of this correlation you are testing the null hypothesis that states there is zero correlation in the population. The requirements for using the Spearman rho are as follows :

1. Ordinal data

2. Two variables

3. Each subject in the study ranked separately on each variable

The formula for the Spearman rho is:

The terms used to find the Spearman rho have the following meanings: N = number of individuals in the group , D = difference between the ranks in the column labeled R ₁ and the column labeled R ₂ , = Spearman rank coefficient, and & pound ; D ² = square each difference and then find the sum.