## Elementary Statistics (12th Edition)

We can see that as time increases, the distance increases, hence the rank correlation is neagtive and is $\pm1$, hence $r_s=-1$. We find the critical values for $n=6$ in the table: $r_s(0.05)=\pm0.886.$ If $r_s(0.05)$ is in the rejection region, we reject the null hypothesis. $-1\lt-0.886$, hence we reject the null hypothesis. Therefore there seems to be correlation.