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

Class Interval

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

Tally Mark 9

9

66 – 71

////

4

72 – 77

///

3

78 – 83

//

2

84 - 89

//

2

Total 

20





9th Grade Math

From Class Interval to HOME PAGE




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.



New! Comments

Have your say about what you just read! Leave me a comment in the box below. Ask a Question or Answer a Question.




Share this page: What’s this?

Recent Articles

  1. 5th Grade Prime and Composite Numbers | Definitions | Examples | Math

    Mar 21, 25 12:18 AM

    5th grade prime and composite numbers

    Read More

  2. 14 Times Table | Read and Write Multiplication Table of 14| Video

    Mar 20, 25 04:03 PM

    14 Times Table
    In 14 times table we will learn how to read and write multiplication table of 14. We read fourteen times table as:One time fourteen is 14 Two times fourteen are 28 Three times fourteen are 42

    Read More

  3. 5th Grade Test of Divisibility Rules | Divisibility Rules From 2 to 12

    Mar 20, 25 04:00 PM

    In 5th grade test of divisibility rules we will learn about the exact divisibility of a number by the numbers from 2 to 12. The digit in the ones place should be 2, 4, 6, 8 or 0.

    Read More

  4. 5th Grade Even and Odd Numbers | Definitions | Examples

    Mar 20, 25 02:45 AM

    Numbers which are exactly divisible by 2 are even numbers. For example. 2,4,6,8,20,48,88, etc. are even numbers. They are multiples of 2. Numbers which are not exactly divisible by 2 are odd numbers…

    Read More

  5. 5th Grade Factors and Multiples | Definitions | Solved Examples | Math

    Mar 20, 25 01:02 AM

    Prime Factor of 312
    Here we will discuss how factors and multiples are related to each other in math. A factor of a number is a divisor which divides the dividend exactly. A factor of a number which is a prime number is…

    Read More