## Graphical representation of Data | Bar Graphs

 Image Credit: Pixabay.com

# Graphical / Visual representation of Data

Graphical representation of Data is easier to understand and interpret.
Data can be represented graphically through following methods:
➢ Pictographs
➢ Bar Graphs
➢ Double Bar Graphs
➢ Pie Charts or Circle Charts
➢ Histograms
➢ Line Graphs
They are easier to read and analyse.

## Pictograph

➢ A pictograph represents data through pictures or symbols of objects.
➢ It should be mentioned on the graph as how many unit one symbol or picture stand for.
➢ Sometimes it can be time consuming and difficult to draw.

#### (Ex-9.1) Q5

The number of girl students in each class of a co-educational middle school is depicted by the pictograph :

Observe this pictograph and answer the following questions :

(a) Which class has the minimum number of girl students?

(b) Is the number of girls in Class VI less than the number of girls in Class V?

(c) How many girls are there in Class VII?

#### Ans

(a). Class VIII

(b). No

(c). Number of pictures in row of class VII = 3

One picture = 4 girls

∴ Number of girls in class VII = 3×4 = 12

# Bar Graphs

A bar graph is a pictorial representation of data in which usually bars (rectangles) of uniform width are drawn with equal spacing between them on either horizontal or vertical axis depicting the variables, then the length of each bar represents the value of the corresponding variable.

### Scale

Scale is the quantity we choose to represent through one unit length on the graph .

➧ The length of the bars should always be drawn in proportion with the scale.

i.e. if on scale, one unit length (let 1 cm) represent 10 m then 2 cm will represent 20 m and so on.

➧ For data with smaller numbers we normally choose unit length to represent unit quantity.

➧ To show larger numbers we need larger scale.

## Horizontal Bar Graph

Bars are drawn horizontally. i.e. on x-axis at equal space.

Value is plotted on y-axis for suitable scale.

Variable should be mentioned below the bar on x axis.

#### (Ex9.3)Q3

Bar graph above shows the marks obtained by a student in an examination in different subjects.

(a) What information does the bar graph give?

(b) Name the subject in which Aziz scored maximum marks.

(c) Name the subject in which he has scored minimum marks.

#### Ans

(a) Marks obtained by Aziz in an examination in different subjects.

(b) Hindi (longest bar)

(b) Social Studies (shortest bar)

## Vertical Bar Graph

Bars are drawn vertically i.e. on y-axis at equal space.

Value is plotted on x-axis for suitable scale.

Variable should be mentioned at the left side of the bar on y-axis.

#### (Ex9.3) Q2

Bar graph which showing the sale of shirts in a ready made shop from Monday to Saturday.

(a) What information does the above bar graph give?

(b) What is the scale chosen on the horizontal line representing number of shirts?

(c) On which day were the maximum number of shirts sold? How many shirts were sold on that day?

(d) On which day were the minimum number of shirts sold?

(e) How many shirts were sold on Thursday?

#### Ans

(a) Number of shirts sold per day in the given week.

(b) 1 unit length = 5 shirt

(c) Saturday (longest bar), number of shirts sold on this day = 60

(d) Tuesday (shortest bar)

(e) 35

#### (Ex9.3)Q1-

Bar graph showing the amount of wheat purchased by government during the year 1998-2002.

write down your observations. In which year was

(a) the wheat production maximum?

(b) the wheat production minimum?

(c) What is the scale chosen on the vertical line representing number of shirts?

#### Ans

(a) 2002

(b) 1998

(c) 1 unit length = 5000 tonnes

## ↓Class 7

Double bar graph shows two sets of data simultaneously.

We can combine two (or more) bar graphs representing similar data to compare them at a glance, this type of graph is called double graph.

In double bar graph below, number of watches tested for water resistance is compared to number of watches leaked in that test.

#### Try These

Q. The bar graph shows the result of a survey to test water resistant watches made by different companies. Each of these companies claimed that their watches were water resistant. After a test the above results were revealed.

(a) Can you work out a fraction of the number of watches that leaked to the number tested for each company?

(b) Could you tell on this basis which company has better watches?

#### Ans

(a) 20/40 = 1/2 for company A

10/40 = 1/4 for company B

15/40 = 3/8 for company C

25/40 = 5/8 for company C

(b) Company B has better watches where ratio of watches leaked to ratio of watches tested is lowest. It is also evident from the graph.