Answer
$M_D$ is the median of the differences between the values of the population 1, $X_i$, and the corresponding values from the population 2, $Y_2$.
$D_i=X_i-Y_i$, that is:
$D_1=X_1-Y_1$
$D_2=X_2-Y_2$
$D_3=X_3-Y_3$
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Work Step by Step
Given above.
