Measuring an Electron Spin

Classical Mechanics

A electron spin in quantum mechanics is given by the superposition state:

$\large |\Psi\rangle = \frac{i}{2} |\uparrow\rangle + \dfrac{\sqrt{3}}{2} |\downarrow\rangle.$

What is the probability of measuring the spin in the $z$ -direction to have value equal to $-\dfrac{\hbar}{2}$ ?