To find the ratio of the number of students who do not have a pet to the number of students who have a pet, we can use the given values.
- Number of students who have a pet: 27
- Number of students who do not have a pet: 14
The ratio of students who do not have a pet to those who have a pet is:
\[ \text{Ratio} = \frac{\text{Number of students without pets}}{\text{Number of students with pets}} = \frac{14}{27} \]
This ratio can be expressed as "14:27".
Therefore, the correct answer is 14:27.