Answer
$T\gt w_{\frac{α}{2}}$: null hypothesis is not rejected.
There is not enough evidence to conclude that $M_x\lt M_y$.
Work Step by Step
Left-tailed test.
Small-sample case:
$T=S-\frac{n_1(n_1+1)}{2}=180-\frac{13(13+1)}{2}=180-91=89$
Critical value:
$w_{\frac{α}{2}}=w_{0.025}=71$
(According to table XIII, for $n_1=13$, $n_2=17$ and $α=0.05$)
Since $T\gt w_{\frac{α}{2}}$, we do not reject the null hypothesis.
