Question

O students
Solution :
No. of students
f
:
Steps : 1. Select assumed mean (A), A = 30 in the above example.
2. Calculate the deviations from assumed mean i.e., X - A = d.
3. Multiply deviations by frequency and get fd.
4. Add the product of deviations and frequency and find fd.
5. Use the following formula :
short-cut method. All deviations taken from assumed mean are divided by common factor.
Measures of Central Tendeney | 107
Marks
d=x-A
(x - 30)
fd
10
15
- 20
- 300
20
10
- 10
- 100
30 (A)
40
0
0
40
20
10
200
50
15
20
300
Ef=100
fd = 100
x= A+
Σfa
Σf
100
= 30+ = 30+1=31
100
Average marks of students = 31.
Ans.
If
Step-deviation Method : We can further simplify arithmetic calculations done by the
Symbolically, by assuming 20​

Answer 1

Answer:

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