Question

The following data gives the information on the observed lifetimes (in hours) of 225 electrical components :

Lifetimes (in hours)	0-20	20-40	40-60	60-80	80-100	100-120
Frequency	10	35	52	61	38	29

Answer 1

The class 60-80 has maximum frequency. So, it is the modal class.

∴ l = 60, f₁ = 61, f₀ = 52, f₂ = 38 and h = 20

Hence, the modal lifetimes of the electrical components = 65.625 years