ICSE Class 9 Maths Chapter 18 Graphical Representation of Statistical Data

Graphical Representation of Statistical Data

Points To Remember

1. Graphical Representation of Statistical Data. Through pictures, diagrams etc., we can represent the statistical data. There are various types of graphs:

(1) Bar graph

(2) Histogram

(3) Frequency polygon.

(1) Bar graph or Bar chart. In bar graph, bars of uniform width are drawn with heights according to the data given. The gap between the two bars should be kept the same.

(2) Histogram. A histogram is a graphical representation of a frequency distribution in an exclusive form in form of rectangles with class intervals as bases i.e. on x-axis and corresponding frequencies as heights i.e. on y-axis. There is no gap between any two successive rectangles.

Note.

(1) If the given frequency distribution is in inclusive form, convert it into exclusive form.

(2) The scale chosen for both the axes need not be the same.

(3) Frequency polygon. The mid-points of the adjacent tops of the rectangles of a histogram are joined by the line segments. The mid-point at each end are joined to the immediately lower or higher mid-points at x-axis. Thus, we obtain a polygon which is called frequency polygon.

Teacher's Note

Understanding how to visualize data through graphs and histograms helps us interpret real-world information like weather patterns, population statistics, and sports performance data more easily.

Exercise 18

Q. 1. Given below is the maximum age of some of the animals.

Draw a bar chart to represent the above data.

Sol. We will take name of animals along x-axis and age (in year) along y-axis. Take 1 cm = 10 years.

Teacher's Note

Bar charts are commonly used in news reports and presentations to compare different categories, such as comparing the lifespans of different animals or sales figures across different months.

Q. 2. Construct a histogram for the following frequency distribution:

Sol. We will take class intervals along x-axis and frequency along y-axis. Below is given histogram of the given data. Take 1 cm = 1 frequency.

Teacher's Note

Histograms help us see the distribution of data at a glance, such as how many students scored in different grade ranges or how many people fall into different age groups.

Q. 3. Construct a histogram for the following frequency distribution:

Sol. We will take daily earnings (in Rs.) along x-axis and no. of workers along y-axis. Below is given a histogram of the given data. Scale: 1 cm = 2 workers.

Teacher's Note

Histograms of income distribution help economists and businesses understand economic inequality and plan appropriate wage policies for workers.

This is a preview of the first 3 pages. To get the complete book, click below.