Question

Class mark of a particular class is 6.5 and class size is 3 then class interval is:

• A. $5-8$
• B. $6.5-9.5$
• C. $3.5-6.5$
• D. $4-7$

Answer 1

Answer: (A)

$5-8$

Let the a be the lower limit of the class interval

Class size of the class interval =3

$\therefore$ Upper limit of the class interval$=a+3$

Class mark=6.5

$\therefore \frac{a+a+3}{2}=6.5$

$\Rightarrow 2a+3=6,5\times 2$

$\Rightarrow 2a=13-3$

$\Rightarrow 2a=10\Rightarrow a=\frac{10}{2}=5$

$\therefore a+3=5+3=8$

Hence class interval= $5-8$