Page 85 - Mathematics Class - IX

Unit 6 Statisticsatistics
St

ACTIVITY 6.1

OBJECTIVE
To draw histograms for classes of equal width and varying widths.

MATERIALS REQUIRED

Graph papers A pair of scissors Adhesive
Geometry box with pencil Sketch pens

PRE-REQUISITE KNOWLEDGE
1. Concept of data collection 2. Concept of data representation

THEORY

Histogram: A histogram is a graphical representation of a grouped frequency distribution with continuous classes
in the form of rectangles with class intervals as bases and the corresponding frequencies as height.

Histogram is commonly used to show frequency distribution.

PROCEDURE
1. Collect any data from your surroundings such as heights/uniform size of students in a class and make a
frequency distribution table.

2. Make two tables as shown here:
Case A: For classes of equal widths.

Class a – b b – c c – d d – e e – f f – g g – h

Frequency f f f f f f f
1 2 3 4 5 6 7

Case B: Here, the class sizes are different, so calculate the modified frequency for each class by using the
formula:
Minimumclass size ×Frequency
Modified frequencyofclass =
Classsizze of this class

So, the modified frequency distribution table is as under:

Class a – b b – c c – d d – e e – f f – h
(width x) (width x) (width x) (width x) (width x) (width 2x)

Frequency f f f f f f
1 2 3 4 5 6

Modified frequency F F F F F F
1 2 3 4 5 6

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