Answer
Amplitude= $\dfrac{1}{2}$
Period= $\dfrac{4\pi}{3}$
Work Step by Step
Recall:
For $y=A\cos{(ωx)}$, we have:
$\text{Amplitude}=|A|\quad \quad \text{and} \quad \quad \text{Period}=T=\frac{2\pi}{ω}$
In $y=-\frac{1}{2}\cos \left(\frac{3}{2}x\right)$ we have $A=-\frac{1}{2}$ and $\omega=\frac{3}{2}$, so
Amplitude =$|A|=|-\frac{1}{2}|=\frac{1}{2}$
Period $T=\frac{2\pi}{\omega}=\dfrac{2\pi}{\frac{3}{2}}=\dfrac{4\pi}{3}$
