The less than method of writing classes is used for records that contain fractional values ​​or continuous variables such as those in Table 1.

We will create a frequency table and then calculate the relative frequencies and percentage for all classes.

Choose 5 for the number of classes.

Class width =

Highest Score – Lowest Score
/.
Number of classes

Class width =

15 – 1
/.
5

Class width =

14th
/.
5

= 2.8

The class width can be approximately 3. We can use 1 as the lower bound of the first grade.

The upper limit of the first class must be 4

1-4

4-7

7-10

10-13

13-16

## Important thing to keep in mind when using the less than method to write classes

Note that the Upper, higher The limit of a class is also that lower Next class limit.

This is different from the procedure for discrete variables. For discrete variables, your classes will look more like option 1.

However, option 1 does not contain values ​​between 3 and 4, such as B. 3.4

Therefore, the upper bound of one class must be the lower bound of the next class to ensure that all values ​​are included.

Option 2 includes all values. However, it has 7 classes as opposed to 5.

Option 1

1-3

4-6

7-9

10-12

13-15

Option 2

1-3

3-5

5-7

7-9

9-11

11-13

13-15

The correct However, the way to write the classes is like this.

1 to less than 4

4 to less than 7

7 to less than 10

10 to less than 13

13 to less than 16

To find the frequency of the first grade, simply count how many numbers are between 1 and 4, starting with 1 and ending with a number less than 4

To find the frequency of the second grade, simply count how many numbers are between 4 and 7, starting with 4 and ending with a number less than 7

And so on.

The frequency table is shown below along with the relative frequency and percentage.

To find the relative frequency of the first grade, simply divide 12 by 30.

To find the percentage of the first grade, simply multiply the relative frequency by 100

To find the relative frequency of the second grade, simply divide 7 by 30.

To find the percentage of second grade, simply multiply the relative frequency by 100

and so on.