Spearman's rank correlation is a technique which is used to examine the power and direction of the relation among any two set of variables. Spearman correlation of +1 or -1 arises when every variable is a monotone function of other variable.
σ = Sumation of differences d = Differences n = Number of Datas R = Rank Value
Assume that there are two sets available namely, A and B.Values entered for Set A are '1, 5, 2, 5, 2' and values given for Set B are '2, 2, 3, 1, 3'. Calculate the Spearman rank correlation for the given values?
Spearman Rank Correlation Value (R)
Substitute the given values in the Rank Value (R) formula, Rank Value (R) = 1 - ( (6 X σd2) / (n3 - n) ) = 1 - ( (6 X 26.5) /(125-5)) = 1 - 1.325 R = -0.325
The result is a negative value. So according to the below table, the value -0.325 is considered as a weak negative correlation value.
|Table of Rank value and its correlation conclusion|
|R Value||Correlation Conclusion|
|between -1 and -0.5||Strong negative|
|between -0.5 and 0||Weak negative|
|between 0 and 0.5||Weak positive|
|between 0.5 and 1||Strong positive|