Question

Following table represents literacy rate of 35 cities in percentage.

Literacy rate (in %)	45-55	55-65	65-75	75-85	85-95
Number of cities	3	10	11	8	3

Find mean literacy rate.

Answer 1

Let assumed mean (A) 70

Class size (h) = 55 – 45 = 10

By step deviation method

Mean () = A + \(\left( \frac { { \Sigma f }_{ i }{ u }_{ i } }{ { \Sigma f }_{ i } } \right)\) × h

⇒  = 70 + \(\frac { -2 }{ 35 }\) × 10 = 70 + \(\frac { -20 }{ 35 }\)

= 70 + (-0.57) = 70 – 0.57 = 69.43

Thus, mean literacy rate = 69.43%