The blood groups of 30 students of Class VIII are recorded as follows: A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O, A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O. 

Represent this data in the form of a frequency distribution table. Which is the most common, and which is the rarest, blood group among these students?

For representing the given data in the frequency distribution table we proceed as follows,

First we find each of the blood group occured how many times if A occured 9 times then 9 is the frequency of the blood group A 

Thus, continuing in this way we draw the table of frequency distribution as, 

So, the table shows that, 

The most common blood group is with highest frequency which is blood group O

The rarest blood group is with lowest frequency which is blood group AB