Presenting Data in Bar Graphs – Statistics

Presenting Data in Bar graphs

In a bar graph, there are usually rectangular bars which explain value of observation and its frequency. Height/length of the bar states frequency of observation drawn. Bar graph explains data which is presented in frequency table.
Example 1:
Draw bar graph from data in the following frequency table.

Solution:
Observation values are placed on x axis, and their frequencies are placed on y axis. To each observation values, we draw a bar with its height equals to its frequency. The following is the bar graph that be intended.

Example 2:
The following table presents the result of survey done by a Survey-Company about figures who are considered as superior to be director of a public company. Draw the bar graph of the following data.

Solution:
On bar graph, figures are placed on x axis, and the number of people who chose that figure (frequency) are placed on y axis. The graph is shown below.

Bar Graphs
In bar graphs, only the length of the bars are taken into consideration. To draw a bar graph, we first mark equal lengths for the different classes on the axis, i.e., x-axis.

On each of these lengths on the horizontal axis, we erect (vertical) a rectangle whose heights is proportional to the frequency of the class.

Bar graphs and frequency tables

Data can be represented with a frequency table or with a bar graph. Each bar represents a group of data and the bars can be compared to each other. Bar graphs must be labelled on one axis and show the numbering on the other axis.

Example 3:
In a Geography class, 23 learners completed a test out of 10 marks. Here is a list of their results:
4; 1; 2; 2; 6; 9; 6; 10; 6; 8; 9; 6; 7; 7; 8; 4; 6; 6; 5; 7; 9; 10; 6.
We can use a frequency table to record this data.

We can also make a bar graph to show this data. Use the marks from 1 to 10 on the horizontal axis. Use the number of learners who got that score on the Vertical axis. The number of learners is the frequency.

Other Examples

Intruction: Choose the one correct answer for each question.
Use the data of the following graph to answer question 1-3.
Andi recorded the number of siblings from his classmates. The results that his obtained is presented in the following graph.

Asume x-axis serves the number of sibling(s) and y-axis serves the number of Andy’s classmates who have got the respective sibling(s).
1. The number of students who have 3 siblings is ….
A. 1 B. 2 C. 3 D. 4 E. 5
Key: E
2. Most of Andy’s classmates have … siblings.
A. 0 B. 1 C. 3 D. 4 E. 5
Key: B
3. The number of Andy’s classmates is …
A. 33 B. 34 C. 35 D. 36 E. 37
Key: C, solution:
4+14+9+5+2+1=35

Use the data of following graph to answer question 4-6.
The examination results of two different classes are presented in following graph.

Assume x-axis serves respective scores and y-axis serves the number of students who have got the respective scores.
4. The number of students in class B who get 8 is ….
A. 0 B. 1 C. 2 D. 3 E. 4
Key: C
5. The number of students in class A and B is ….
A. 45 B. 46 C. 47 D. 48 E. 49
Key: C, solution:
3+(5+4)+(3+5)+(6+4)+(1+6)+(4+2)+2+2=47

6. Students in class B mostly get ….
A. 4 B. 5 C. 6 D. 7 E. 8
Key: D
Students in class B mostly get score 7, there are six students written in y-axis.

Instruction: Solve the following problem correctly.
7. Data in the following frequency table are the weekly wages of 50 employees in a company.

Draw the bar graph of this data.
Solution: