frequency distribution student ages

Question

age          A=event the student selected is under 21
17            B=event the student selected is over 30
18            C=event the student selected is in his or her 20s, and
19            D=event the student selected is over 18
90
21
22           
23
24
35
36   
 
frequency
1
1
9
7
7
5
3
4
1
1
1
 
 
 
I'm really confused about the outcome of (b). it's asking student selected over 30 and there are two students over 30, nut the answer is (A&D) Please explain why (A&D) is the answer and how did they come up with that.

Answer 1

There is one extra frequency count with no age specified. That might be what your teacher is looking for.  There is something wrong with the numbers given, an extra frequency count with no corresponding age. That's what the x is for at the bottom of the age column.  You don't know how old that person is.

First create one table with two columns:  Age            Frequency

 

and move the 90 year olds after the 36 year old

 

It looks like this

 

Age    Frequency

 

17       1

18       1

19       9

21       7

22       5

23       3

24       4

35       1

36       1

90       7

X         1