Graphical Representation of Data

The information collected is called ‘Data’. Its singular form is called ‘Datum’. Data can be facts or figures, collected with a definite purpose. The process of gathering information is called ‘Collection of Data’. All types of facts and observations that are collected for some analysis is

called statistical data. The way to present the collected data in an understandable and a meaningful form is called ‘Presentation of Data’. Data is also represented graphically in many ways.

A bar graph is a pictorial representation of discrete data. In bar graph, data is represented by separate rectangular bars, each having uniform width.

This type of display allows us to compare groups of data, and make generalisation about the data quickly.

A histogram is a graph used to represent the continuous class intervals. The frequency of the classes is represented through the adjacent rectangles. They form a set of vertical bars whose area is proportional to the frequency they represent. There are two cases for constructing a histogram: when equal class intervals are given and when unequal class intervals are given.

A frequency polygon is a graph, which is constructed by joining the midpoints of the top of all the rectangles of a histogram.

Mid-points of class intervals are called class marks. Class mark is the mean of upper limit and lower limit.

Key words: Features of a bar graph, Reading a bar graph, Features of a histogram, Drawing frequency polygon without using histogram.

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