To find the relative frequency for the class with the lower class limit of 15, we first need to calculate the total number of students and then determine the relative frequency for that specific class.

Step 1: Calculate the Total Number of Students

Sum the number of students in all the age groups:

$\text{Total number of students} = 2 + 9 + 5 + 3 + 2 + 4 = 25$

Step 2: Find the Relative Frequency for the Class 15-18

The relative frequency is calculated by dividing the number of students in the specific class by the total number of students, then multiplying by 100 to express it as a percentage.

$\text{Relative frequency} = \left(\frac{\text{Number of students in the class}}{\text{Total number of students}}\right) \times 100$

For the class 15-18:

$\text{Relative frequency} = \left(\frac{2}{25}\right) \times 100 = 8\%$

So, the relative frequency for the class with the lower class limit of 15 is 8.0%.

Would you like further details on this problem or have any questions?

Here are 5 related questions you might find interesting:

1. How do you calculate the relative frequency for the other age groups?
2. What is the cumulative frequency for the age group 15-18?
3. How do you determine the class with the highest relative frequency?
4. Can you explain the difference between relative and cumulative frequencies?
5. How would the relative frequencies change if one more student were added to the 19-22 age group?

Tip: Always double-check your calculations, especially when converting fractions to percentages, to ensure accuracy.