Answer
$T\gt T_α$: null hypothesis is not rejected.
There is not enough evidence to conclude that $M_D\lt0$.
Work Step by Step
Left-tailed test.
Test statistic: $T=T_+=33$
Critical value: $T_α=30$
(According to table XII, for $n=15$ and $α=0.05$)
Since $T\gt T_α$, we do not reject the null hypothesis.
