Determine the probability of the given opposite event.
What is the probability of rolling a fair die and not getting an outcome less than 4 ?

The probability of rolling a fair die and not getting an outcome less than 4 is $\square$.
(Type an integer or a simplified fraction.)

Step 1 ：The outcomes of rolling a fair die are 1, 2, 3, 4, 5, and 6.

Step 2 ：The outcomes less than 4 are 1, 2, and 3.

Step 3 ：So, the outcomes not less than 4 are 4, 5, and 6.

Step 4 ：The probability of an event is the number of favorable outcomes divided by the total number of outcomes.

Step 5 ：In this case, the total number of outcomes is 6 (since a die has 6 faces), and the number of favorable outcomes (not getting an outcome less than 4) is 3.

Step 6 ：So, the probability is \( \frac{3}{6} \), which simplifies to \( \frac{1}{2} \).

Step 7 ：Final Answer: The probability of rolling a fair die and not getting an outcome less than 4 is \( \boxed{\frac{1}{2}} \).