Class 6 – Statistics
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Introduction: Initially, data used to be represented pictorially through pictographs in which picture symbols were used to represent a certain number of items and then each observation was shown by drawing the proportional number of pictures. But the method of drawing pictographs was time consuming and so it did not turn out to be very useful. However, columngraphs are simple to draw, convenient to read and provides easy comparison of the given data. Columngraphs (or bar diagrams) consist of rectangles of equal width and varying heights depending upon the numerical data. Also, the distance between each pair of consecutive rectangles is kept the same. The following examples will make the idea more clear. In bar graph, entries are taken on xaxis and frequencies of entries are taken on yaxis.
Example: The marks obtained by Rohit in his annual examination are shown below:
Draw a bardiagram to represent the above data.

Solution: Reading a bardiagram: Example: Given below is a columngraph showing the heights of six mountain peaks. Read the above diagrams and answer the following questions: i) Which is the highest peak and what is its height? ii) Find the ratio of the heights of the highest peak and the lowest peak. iii) Write the names of the peaks in ascending order of their heights. 

Which is second highest peak and what is its height?
Solution: It is quite evident that the heights of the bars in the given bar diagram represents the heights of the mountain peaks. Clearly the highest bar represents the highest peak while the lowest bar represents the lowest peak.
Thus, we have:
i) Mount Everest is the highest peak and its height is 8800 m.
ii) Height of the highest peak = 8800 m
Height of the lowest peak = 6000 m
∴Required ratio = 8800 : 6000 = 22 : 15
iii) The peaks in ascending order of their heights are:
Annapurna(6000 m), Himadri (6500 m), Nanda devi (7500 m),
Nanga parbat (8200 m), Kanchenjung (8600 m), Mount Everest (8800 m).
iv) The height of Kanchenjung is next to that of Mount Everest. So the second highest peak is Kanchenjung. Its height is 8600 m.
Example: 60 students from a certain locality use different modes of travel to school as given below:
Mode of travel 
Car 
Bus 
Moped 
Bicycle 
Rickshaw 
Number of students 
6 
15 
10 
18 
11 
Drawa bar diagram to represent the given data.
Solution: Take the mode of travel along the xaxis and the number of students along the yaxis.
Along the yaxis, take 1 cm to represent 2 students. Thus, we may draw the graph for the above data as shown below.
A histogram is similar to a bar graph. In it the bars are attached.
Draw a histogram for the following data.
Subject 
Hindi 
English 
Maths 
Science 
Social 
Marks 
130 
140 
170 
110 
120 
This is also a bar diagram, when the grouped data is given.