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


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.



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.



Share this page: What’s this?

Recent Articles

  1. 2nd grade math Worksheets | Free Math Worksheets | By Grade and Topic

    Dec 06, 23 01:23 AM

    2nd Grade Math Worksheet
    2nd grade math worksheets is carefully planned and thoughtfully presented on mathematics for the students.

    Read More

  2. Rupees and Paise | Paise Coins | Rupee Coins | Rupee Notes

    Dec 04, 23 02:14 PM

    Different types of Indian Coins
    Money consists of rupees and paise; we require money to purchase things. 100 paise make one rupee. List of paise and rupees in the shape of coins and notes:

    Read More

  3. Months of the Year | List of 12 Months of the Year |Jan, Feb, Mar, Apr

    Dec 04, 23 01:50 PM

    Months of the Year
    There are 12 months in a year. The months are January, February, march, April, May, June, July, August, September, October, November and December. The year begins with the January month. December is t…

    Read More