Question:
The class marks of a frequency distribution are 15, 20, 25, 30, .. . The class corresponding to the class marks 20 is
(a) 12.5−17.5
(b) 17.5−22.5
(c) 18.5−21.5
(d) 19.5−20.5
Solution:
(b) 17.5
We are given frequency distribution 15, 20, 25, 30,...
Class size = 20
Class marks = 20
Now,
Lower limit $=\left(20-\frac{5}{2}\right)=\frac{35}{2}=17.5$
Upper limit $=\left(20+\frac{5}{2}\right)=\frac{45}{2}=22.5$
Thus, the required class is 17.5
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