Similarly, imagine an electron E. Let us write $$E = \frac{30}{100} \times \uparrow + \frac{70}{100} \times \downarrow$$ to represtent that there is a 30% chance of us measuring a spin of $$+\frac{1}{2} \uparrow$$ and a 70% chance of us measuring a spin of $$-\frac{1}{2} \downarrow$$.