Question

The class marks of a frequency distribution are given as follows : 15, 20, 25, ........ .The class corresponding to the class mark 20 is _________.

Answer 1

The given class marks are 15, 20, 25,... . Here, the classes are uniformly spaced. So, the class width is the difference between any two consecutive class marks.

Class width = 20 − 15 = 5

If a is the class mark of a class interval of width h, then the lower and upper limits of the class interval are $a-\frac{h}{2}$ and $a+\frac{h}{2}$, respectively.

Here, a = 20 and h = 5.

∴ Lower class limit of the class having class mark 20 = $20-\frac{5}{2}=20-2.5=17.5$

Upper class limit of the class having class mark 20 = $20+\frac{5}{2}=20+2.5=22.5$

So, the class corresponding to the class mark 20 is 17.5–22.5.

The class marks of a frequency distribution are given as follows : 15, 20, 25, ........ .The class corresponding to the class mark 20 is __17.5–22.5__.