Answer
amplitude $\frac{1}{2}$, period $ 4\pi$, no vertical translation, and phase shift $2\pi$ to the left.
Work Step by Step
Given $y=-\frac{1}{2}\ sin(\frac{1}{2}x+\pi)=-\frac{1}{2}\ sin\frac{1}{2}(x+2\pi)$, we can find the following: amplitude $\frac{1}{2}$, period $p=\frac{2\pi}{1/2}=4\pi$, no vertical translation, and phase shift $2\pi$ to the left.
