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

Determine the modal lifetimes of the components

As per the question:

Modal class = 60-80

l = 60

h = 20

f₁ = 61

f₀ = 52

f₂ = 38

$Mode = 60+(\frac{61-52}{(2\times61)-52-38})\times20$

$Mode = 60+\frac{9\times20}{32}$

Or Mode = 60 + 5.625

or Mode = 65.62

Thus, the modal lifetime of 225 electrical components is 65.62 hours

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