Representation of Data

    We have learnt how to collect the information and how to organize it using a frequency table. To represent the study of this data, we can draw graphs for this data. 
    Pictographs and bar graphs are simple ways of representing this data. 

    1.    Pictograph : A pictograph represents data through pictures of objects. It helps answer the questions on the data at a glance. We represent the data using pictures as following example : 
        Ex.    A cupboard has five compartments. In each compartment a row of books is arranged. The details are indicated in the adjoining table :

By seeing above pictograph we can easily get information that Row 4 has the greatest number of books. Row 3 has the least number of books and no Row which does not have books.
        Interpretation of a Pictograph :
        Ex.1     The following pictograph shows the number of absentees in a class of 30 students during the previous week :

        (a)     On which day were the maximum number of students absent?
        (b)     Which day had full attendance?
        (c)     What was the total number of absentees in that week?
        Sol : (a)Maximum absentees were on saturday. (There are 8 pictures in the row for saturday; on all other days, the number of pictures are less). 
            (b)     Against thursday, there is no picture, i.e. no one is absent. Thus, on that day the class had full attendance.
            (c)     There are 20 pictures in all. So, the total number of absentees in that week was 20.

Ex.2     A survey was carried out on 30 students of class VI in a school. Data about the different modes of transport used by them to travel to school was displayed as pictograph. What can you conclude from the pictograph?

Sol.  From the pictograph we find that:
        (a) The number of students coming by private car is 4.
        (b) Maximum number of students use the school bus. This is the most popular way.
        (c) Cycle is used by only three students.
        (d) The number of students using the other modes can be similarly found.

Drawing a Pictograph :
    Ex.3    The following are the number of electric bulbs purchased for a lodging house during the first four months of a year.

2.    Bar Graph: Sometimes representing data by pictograph is difficult due to large data. There is another way of representing data visually is Bar Graph. Bars of uniform width can be drawn horizontally or vertically with equal spacing between them and then the length of each bar represents the given number. Such a method of representing data is called a bar diagram or a bar graph. 

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