need to find the median:

Group Frequency

0-4 2

5-9 3

10-14 7

15-19 5

20-24 3

need to find the median:

Group Frequency

0-4 2

5-9 3

10-14 7

15-19 5

20-24 3

Group Frequency

0-4 2

5-9 3

10-14 7

15-19 5

20-24 3

There are 2+3+7+5+3=20 points, so the median is the average of the 10th & 11th. But you have classes, not the actual points, so you have to start at the bottom of the interval (10-14, probably 9.5). The 10th point is 5th (of 7) in the interval & the interval is 5 wide, so its 9.5+(5/7)(5).