Calculation of Arithmetic Mean – Discrete
Series
Mean = (å fX)/N
Where:
f = frequency
X = the variable in question
N = total no. of observations (i.e., å
f)
- Multiply the frequency of each row with the variable
and obtain the total å
fX.
- Divide the total obtained in step 1 by the no.
of observations (i.e., the total frequency).
Q. 3. From the following the data of the marks
obtained by the 60 students of a class, obtain the
average marks.
Marks |
No of Students
|
Marks |
No. of Students
|
20
|
8 |
50 |
10 |
30
|
12 |
60 |
6 |
40
|
20 |
70 |
4 |
Solution. Let the marks be denoted by X and
the no. of the students by f.
Marks
X |
No of students
f |
fX |
20
|
8 |
160
|
30
|
12
|
360
|
40
|
20
|
800
|
50
|
10
|
500
|
60
|
6 |
360
|
70
|
4 |
280
|
Total |
N
= 60 |
å
fX = 2,460 |
Mean = å fX/N = 2460/60
= 41.
Hence, the average marks = 41.
|