An agricultural scientist investigated the relationship between the percentage of organic matter in soil ($M$) and the dry weight biomass yield of wheat crops ($Y$) in tonnes per hectare. She sampled 16 fields ($N=16$) and calculated Spearman's rank correlation coefficient ($r_s$) between $M$ and $Y$. Her calculated value was $r_s=0.650$.

She concluded that there was a significant positive correlation and rejected her null hypothesis.

Table 1: Critical values for Spearman’s Rho ($r_s$)

Note: To achieve significance, the calculated value of $r_s$ must be equal to or greater than the critical value in the table.