Answer
$r_s\gt 0.521$: null hypothesis is rejected.
There is enough evidence to conclude that temperature and number of chirps per second are associated.
Work Step by Step
$H_0: X~and~Y~are~not~associated$
versus
$H_1: X~and~Y~are~associated$
See the picture.
$∑d_i^2=1+1+9+0+9+9+1+16+12.25+0+1+2.25+9+4+9=83.5$
$r_s=1-\frac{6∑d_i^2}{n(n^2-1)}=1-\frac{6\times83.5}{15(15^2-1)}=0.851$
Critical values = 0.521 and -0.521
(According to Table XIV, for n = 15 and α(2) = 0.05)
Since $r_s\gt 0.521$, we reject the null hypothesis.
