Answer
$T\lt w_{\frac{α}{2}}$: null hypothesis is rejected.
There is enough evidence to conclude that $M_x\lt M_y$
Work Step by Step
Left-tailed test.
Small-sample case:
$T=S-\frac{n_1(n_1+1)}{2}=210-\frac{18(18+1)}{2}=210-171=39$
Critical value:
$w_{\frac{α}{2}}=w_{0.025}=96$
(According to table XIII, for $n_1=18$, $n_2=16$ and $α=0.05$)
Since $T\lt w_{\frac{α}{2}}$, we reject the null hypothesis.
