Question

Marks of the 100 students are distributed in the grouped frequency distribution.

Marks (Class marks)	70	80	90	100
No. of Students (Frequency)	25	41	7	13

What is the class interval for the group having frequency 13?

• A. 90 - 100
• B. 95 - 105
• C. 80 - 90
• D. 85 - 95

Answer 1

The correct option is B 95 - 105

As class marks or mid points are given, class intervals are to be calculated from the class marks.

Difference between the two successive classes = h = 80 - 70 = 10

If x is the class marks then, Lower and Upper boundary of every class is x - $\frac{h}{2}$ and x + $\frac{h}{2}$

Hence, for the group having frequency 13.

Lower boundary = 100 - $\frac{10}{2}$ = 95

Upper boundary = 100 + $\frac{10}{2}$ = 105

Class interval is 95 - 105