Class Interval

Definition of Class Interval

While arranging large amount of data (in statistics), they are grouped into different classes to get an idea of the distribution, and the range of such class of data is called the Class Interval.

More About Class Interval

  • Class intervals are generally equal in width and are mutually exclusive.
  • The ends of a class interval are called class limits, and the middle of an interval is called a class mark.

  • Class interval is generally used to draw histogram.

Video Examples: Continuity of Function in Interval Examples


Example of Class Interval

      examples of Class Interval
    In the table above, heights of 20 students of a class are divided into classes with the size of each class interval being 5.

Solved Example onClass Interval

Ques: Plant scientists developed different varieties of corns that have a rich content of lysine which is a nutritious animal feed. A group of chicks were given this food to test the quality. Weight gains (in grams) of these chicks after 21 days are as recorded: 380, 321, 366, 356, 349, 337, 399, 384, 410, 329, 350, 340, 324, 396, 412, 420, 382, 318, 344, 438. By constructing a frequency distribution table for 7 classes, find the class interval in which the weight increase is maximum.

    Choices:
    A. 426 - 443
    B. 335 - 351
    C. 318 - 438
    D. 336 - 353
    Correct Answer: D

Solution:

    Step 1: Range of the data = higher value - lower value = 438 - 318 = 120
    Step 2: Width = Range/number of classes = 120/7 = 17.14 � 18
    [Round to the higher value.]
    Step 3: Construct the class limits (weight gains) with width 18, so that the least and the highest values are included.
    Step 4: The class limits, boundaries, tally marks and the frequency for each class (number of tally marks) are shown in the table.
    Step 5:
      example of Class Interval

    Step 6: The class interval in which the weight increase maximum is 336 - 353. [Frequency is more for the class 336 - 353.]

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