Question

Following data represents life period observations of electrical instruments.

Life period (in hrs.)	0-20	20-40	40-60	60-80	80-100	100-120
Frequency	10	35	52	61	38	29

Find mode of life period of instruments.

Answer 1

Here maximum frequency is 61 and its corresponding class-interval is 60 – 80. 

So modal class = 60 – 80.

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

Thus, mode of life period is 65.625 hrs