**Probability** measures the likelihood that an event will occur.

A probability near 0 indicates that an event is **unlikely**.

A probability near 1 indicates that an event is **likely**.

A probability near $\frac{1}{2}$ indicates that an event is **neither unlikely nor likely**.

$\text{Probability of event}=\frac{\text{Outcomes where event occurs}}{\text{Total number of outcomes}}$

First, find the total number of tokens in the bag.

2 + 5 + 3 = 10

Out of the 10 tokens in the bag, 5 of the tokens are blue. Write the probability as a fraction, and simplify if possible.

$\frac{5}{10}=\frac{1}{2}$

So, the probability Haley selects a blue token is $\frac{1}{2}$.