# Class Interval

In order to express raw data in the form of grouped data we use classes (or class intervals) for the values of the variables.

Depending upon the method of grouping data, class intervals can be divided into two categories.

(i) Overlapping Class Intervals: If the values of a variable in a collection of data are positive integers less than 50, we can group the data in five overlapping class intervals: 0 – 10, 10 – 20, 20 – 30, 30 – 40, 40 – 50. These are the groups of values of the variable. In case of overlapping intervals, 0 – 10 is the group containing the values of the variable that are greater than or equal to 0 but less than 10. Similarly, 10 – 20 is the group containing the values of the variable that are greater than or equal to 10 but less than 20.

(ii) Nonoverlapping Class Intervals: If the values of a variable in a collection of data are positive integers less than or equal to 50, we can group the data in five nonoverlapping intervals: 1 – 10, 11 – 20, 21 – 30, 31 – 40, 41 – 50. These are the groups of values of the variable. In case of nonoverlapping intervals, 1 – 10 is the group containing the values of the variable that are greater than or equal to 1 but less than or equal to10. Similarly, 11 – 20 is the group containing the values of the variable that are greater than or equal to 11 but less than or equal to 20.

1. The weights (in kg) of the teachers of s school are recorded as shown below.

60, 65, 63, 70, 65, 62, 65, 63, 64, 60, 68, 58, 62, 65, 63, 65, 64, 60, 62, 63.

If the collection of data be grouped into the class intervals 56 - 59, 59 - 62, 62 - 65, 65 - 68, 68 -71 then answer the following:

(i) What is the type of these class intervals?

(ii) Find the frequency of the class interval 59 - 62.

Solution:

(i) These are overlapping class intervals.

(ii) 3 (Since only 60, 60, 60 fall in this class).

2. The weights (in kg) of the teachers of s school are recorded as shown below.

60, 65, 63, 70, 65, 62, 65, 63, 64, 60, 68, 58, 62, 65, 63, 65, 64, 60, 62, 63.

If the collection of data be grouped into the class intervals 56 - 59, 60 - 63, 64 - 67, 68 - 71 then answer the following:

(i) What is the type of these class intervals?

(ii) Find the frequency of the class interval 59 - 62.

Solution:

(i) These are nooverlapping class intervals.

(ii) 7 (Since only 64, 64, 65, 65, 65, 65, 65 fall in this class).

3. The following are the marks obtained by 20 students of a class:

61, 62, 65, 65, 62, 70, 62, 70, 75, 72, 70, 60, 80, 85, 63, 85, 67, 80, 75, 65.

Prepare a frequency table by taking class intervals

(i) 60 - 65, 65 - 70, etc.

(ii) 60 - 65, 66 - 71, etc.

Solution:

(i)

Class Interval

(Marks Obtained)

Tally Marks

Frequency

60 – 65

6

65 – 70

////

4

70 – 75

////

4

75 – 80

//

2

80 - 85

//

2

85 - 90

//

2

Total

20

(ii)

Class Interval

(Marks Obtained)

Tally Marks

Frequency

60 – 65

9

66 – 71

////

4

72 – 77

///

3

78 – 83

//

2

84 - 89

//

2

Total

20

Didn't find what you were looking for? Or want to know more information about Math Only Math. Use this Google Search to find what you need.

## Recent Articles

1. ### Comparison of Three-digit Numbers | Arrange 3-digit Numbers |Questions

Sep 13, 24 02:48 AM

What are the rules for the comparison of three-digit numbers? (i) The numbers having less than three digits are always smaller than the numbers having three digits as:

2. ### Worksheet on Three-digit Numbers | Write the Missing Numbers | Pattern

Sep 13, 24 02:23 AM

Practice the questions given in worksheet on three-digit numbers. The questions are based on writing the missing number in the correct order, patterns, 3-digit number in words, number names in figures…

3. ### 2nd Grade Place Value | Definition | Explanation | Examples |Worksheet

Sep 13, 24 01:20 AM

The value of a digit in a given number depends on its place or position in the number. This value is called its place value.

4. ### Comparison of Two-digit Numbers | Arrange 2-digit Numbers | Examples

Sep 12, 24 03:07 PM

What are the rules for the comparison of two-digit numbers? We know that a two-digit number is always greater than a single digit number. But, when both the numbers are two-digit numbers

5. ### Worksheet on Two Digit Numbers | Numbers in Words | Two-Digit Numbers

Sep 12, 24 02:09 AM

In worksheet on 2-digit numbers we will write the number which come before, after and in between, write the numerals, write the number names, place value and face value of 2-digit numbers, numbers in…