Question 46

Jambmaths question: 

Class width

3 – 5

6 – 8

9 – 11

Frequency

2

2

2

Find the standard deviation of the above distribution

Option A: 

$\sqrt{7}$

Option B: 

$\sqrt{6}$

Option C: 

$\sqrt{5}$

Option D: 

$\sqrt{4}$

Jamb Maths Solution: 

Class

interval

Mid-class

X

f

fx

D=$x-\overline{x}$

D2

fD2

3 – 5

4

2

8

– 3

9

18

6 – 8

7

2

14

0

0

0

9 – 11

10

2

20

3

9

18

Total

 

 

42

 

 

36

$\overline{x}=\frac{\sum fx}{\sum f}=\frac{42}{6}=7$
$\sigma =\sqrt{\frac{\sum f{{(x-\overline{x})}^{2}}}{\sum f}}=\sqrt{\frac{36}{6}}=\sqrt{6}$

 

Jamb Maths Topic: 
Year of Exam: