Answer
$T\lt T_α$: null hypothesis is rejected.
There is enough evidence to conclude that $M_D\gt0$.
Work Step by Step
Right-tailed test.
Test statistic: $T=|T_-|=16$
Critical value: $T_α=17$
(According to table XII, for $n=12$ and $α=0.05$)
Since $T\lt T_α$, we reject the null hypothesis.
