how to construct a continuous grouped frequency distribution table

Let us understand the mentioned by taking an example

The ages of some residents of a particular locality are given as follows.

7, 28, 30, 32, 18, 19, 37, 36, 14, 27, 12, 8, 17, 24, 22, 2, 21, 5, 21, 36, 38, 25, 10, 25, 9.

We represent such type of data with the help of grouped frequency distribution table.

Let us now see how to draw it.

First of all, we will choose the class interval. In the given data, the minimum value is 2 and the maximum value is 38. We can take the class intervals as 0 – 10, 10 – 20, 20 – 30, 30 – 40 and obtain the number of residents falling in each group. All the given observations get covered in these four classes.

Now, the observations which are more than 0 but less than 10 will come under the group 0 – 10; the numbers which are more than 10 but less than 20 will come under the group 10 – 20 and so on.

We must note one thing, 10 occurs in two classes, which are 0 – 10 and 10 – 20. But it is not possible that an observation can be included in both classes. To avoid this, we adopt the convention that the common observation will belong to the higher class, i.e. 10 will be included in the class interval 10 – 20 and similarly we follow this for the other observations also.

The grouped frequency distribution table will be as follows.

Class intervals

Tally marks

Frequency

0 – 10

5

10 – 20

 

6

20 – 30

 

8

30 – 40

 

6

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