http://www.ck12.org Chapter 5. Measures of Central Tendency
Thus, the mean number of books read by each student can be calculated as follows:
x=
∑x 1 f 1 +x 2 f 2 +x 3 f 3 +...+xnfn
f 1 +f 2 +f 3 +...+fnx=∑( 0 )( 1 )+( 1 )( 6 )+( 2 )( 8 )+( 3 )( 10 )+( 4 )( 13 )+( 5 )( 8 )+( 6 )( 5 )+( 7 )( 6 )+( 8 )( 3 )
1 + 6 + 8 + 10 + 13 + 8 + 5 + 6 + 3
x=∑0 + 6 + 16 + 30 + 52 + 40 + 30 + 42 + 24
60
x=240
60
x= 4The mean number of books read by each student was 4 books.
Example B
Suppose the numbers of books read by each student in Example A were randomly listed as follows. Determine the
mean of the numbers.
0 5 1 4 4 6 7 2 4 3 7 2 6 4 2
8 5 8 3 4 3 6 4 5 6 1 1 3 5 4
1 5 4 1 7 3 5 4 3 8 7 2 4 7 2
1 4 6 3 2 3 5 3 2 4 7 2 5 4 3
An alternative to entering all the numbers into a calculator would be to create a frequency distribution table like the
one shown below:
TABLE5.3:
Number of Books Tally Number of Students (Frequency)
0 | 1(^1) ||||| 6
(^2) ||||||| 8
(^3) |||| |||| 10
(^4) |||| ||||||| 13
(^5) ||||||| 8
(^6) |||| 5
(^7) ||||| 6
8 ||| 3