1. The problem is to correct the frequency of the third group to 10. 2. Frequency refers to how often a particular group or event occurs. 3. If the third group's frequency is given incorrectly, we simply update it to the correct value. 4. Therefore, the corrected frequency for the third group is $10$. 5. This means the third group occurs 10 times in the data or context provided. 6. No further calculations are needed as this is a direct correction.