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 |
| No. of components: | 10 | 35 | 52 | 61 | 38 | 29 |

Determine the modal lifetimes of the components.

Answer 1

From the data given as above its observed that maximum class frequency is 61 which belongs to class interval 60 – 80.

So, modal class limit (l) of modal class = 60

Frequency (f) of modal class = 61

Frequency (f1) of class preceding the modal class = 52

Frequency (f2) of class succeeding the modal class = 38

Class size (h) = 20

Using the formula for find mode, we have

Mode

Thus, the modal lifetime of electrical components is 65.625 hours.