Question

Find the mean and standard deviation of the following frequency distribution by step deviation method.

Class	1-5	6-10	11-15	16-20	21-25	26-30	31-35
Frequency	5	7	18	25	20	4	1

Answer 1

Mean (\(\bar{x}\)) = 1/N∑f₁x₁ = 1/80 x 1360 = 17

Standard deviation (σ) = √(1/N∑f₁(x₁ - \(\bar{x}\))²) 

= √(1/80 x 3320) = √(41.5) = 6.44