Construct a frequency table for the following ages (in years) of 30 students using equal class intervals, one of them being 9-12, where 12 is not included.

18, 12, 7, 6, 11, 15, 21, 9, 8, 13, 15, 17, 22, 19, 14, 21, 23, 8, 12, 17, 15, 6, 18, 23, 22, 16, 9, 21, 11, 16.

Minimum observation = 6


Maximum observation = 23


The classes of equal size covering the given data are:


6-9, 9-12, 12-15, 15-18, 18-21, 21-24, 24-27


So, grouped frequency table will be as given below,


Class



Frequency



6 – 9



5



9 – 12



5



12 – 15



4



15 – 18



6



18 – 21



3



21 – 24



7



7