Apr 15, 2015 · correlation coefficients are 0.93, 0.87, and 0.63 at the depth of 10, 20 and 30 cm consecutively. The resulted coefficients indicate strong positive correlation up to 20 cm depth of soil which blatantly validates the premise of the study. The correlation coefficient calculated above corresponds to Spearman's correlation coefficient. The requirements for computing it is that the two variables X and Y are measured at least at the interval level (which means that it does not work with nominal or ordinal variables).