To find the probability that a randomly selected student from the class is left-handed, we first need to determine the number of left-handed students.
Given:
- Total number of students in the class = 31
- Number of right-handed students = 28
We can calculate the number of left-handed students as follows:
\[ \text{Number of left-handed students} = \text{Total students} - \text{Right-handed students} \] \[ \text{Number of left-handed students} = 31 - 28 = 3 \]
Now, we can calculate the probability of selecting a left-handed student:
\[ \text{Probability (P) of left-handed student} = \frac{\text{Number of left-handed students}}{\text{Total number of students}} = \frac{3}{31} \]
Thus, the probability that a randomly chosen student is left-handed is:
\[ \boxed{\frac{3}{31}} \]