#### Answer

$\frac{1}{2}$

#### Work Step by Step

To calculate probability, we need to divide the number of chances for a certain outcome to occur by the total number of outcomes. In this case, there are $4$ even numbers on the spinner, and $8$ numbers in total. When we divide $4$ by $8$, we get $\frac{1}{2}$, which is the probability of getting an even number.