Question

Why are class boundaries necessary for grouped data?

Answer 1

The class boundaries are used for drawing a histogram to display the data and avoid any confusion.

Explanation:

Class boundaries are needed when we are working with continuous data. They ensure that there is no doubt about which interval a value belongs to.

Without defining class boundaries, we could have the following possible intervals.

`15 - 20`
`20-25`
`25-30`

A problem arises because it is not clear we we would place values of 20 and 25 because they occur in 2 intervals.
But if the intervals are defined with class boundaries there is no doubt.

`15<= x < 20`
`20<=x < 25`
`25<= x <30`

We could also be given the following intervals:

`6-9`
`10-15`
`16- 21`

Again there is an apparent problem, because where would values such as 9.3 or 15.8 lie?

But if the intervals are defined using class boundaries there is no doubt.

`5.5 <=x <9.5`
`9.5<=x<15.5`
`15.5<=x<21.5`

The class boundaries are used for drawing a histogram to display the data.