The following data gives the information of life of 200 electric bulbs (in hours) as follows:

Find the modal life of the electric bulbs.

Observe that, from the given data:

The maximum class frequency, here, is 82 and the class corresponding to this frequency is 80 – 100.

So, this implies that,

Modal class = 80 – 100

Mode of such grouped frequency distribution is given by,

Where,

l = lower limit of the modal class = 80

f₀ = frequency of the class preceding the modal class = 42

f₁ = frequency of the modal class = 82

f₂ = frequency of the class succeeding the modal class = 71

c = size of class interval (the class intervals are same) = 20

∴ Substituting the values l = 80, f₀ = 42, f₁ = 82, f₂ = 71 and c = 20 in the formula of mode. We get

⇒

⇒

⇒

⇒ Mode = 80 + 15.69

⇒ Mode = 95.69

Thus, the modal life of electric bulbs is 94.29 hours.