7. Calculate variance and standard Deviation for the following Data set.
70, 80, 90, 100
Answers
Answer:
Class Interval Mid Value (x) frequency (f) fx fx
2
30−40 35 3 105 3675
40−50 45 7 315 14175
50−60 55 12 660 36300
60−70 65 15 957 63375
70−80 75 8 600 45000
80−90 85 3 255 21675
90−100 95 2 190 18050
n=∑f=50
x
ˉ
=
n
1
∑fx
i
=
50
3082
=61.64
Variance (σ
2
)=
n
1
∑fx
2
−(
x
ˉ
)
2
=
50
202250
−(61.64)
2
=245.5104
Standard deviation (σ)=
245.5104
=15.67