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Kerala Plus One Economics Notes Chapter 14 Presentation of Data
Presentation of Data
The most common form of presenting the data are textual or descriptive presentation, tabular presentation and diagrammatic presentation.
Textual Presentation of Data: This is the method of presenting data in text form. This method of presentation is possible only when the quantity of data is not too large. Following are the two examples of presenting the data in a textual format appeared in news papers.
Tabular Presentation of Data: Tabular presentation is the systematic arrangement of data in rows and columns. In other words, tabulation is a layout of figures in rectangular form with appropriate heading to explain different rows and columns.
Diagrammatic and Graphical Representation of Data: It is the more attractive and eye-catching method of presenting data. This provides the quickest understanding of the actual situation to be explained by data in comparison to tabular or textual presentations. The diagrams are broadly divided into three namely geometric diagrams, frequency diagram and arithmetic line graph. Again, geometric diagrams are classified into bar diagram and pie diagram.
Parts of a Table
A good table should have the following parts.
i) Table Number: Table number is essential for identifying the table; especially when more than one table is presented. It is the table numberthat distinguishes one table from the other. For easy reference, they are numbered according to their order of appearance in the text. It may be placed at the top or at the bottom)
ii) Title: Every table should contain a title, because it narrates about the contents of the table. Just like the table number, the title can also be placed at the top or bottom of the table. The title should be clear, brief, carefully worded, unambiguous and complete. It should be capable of giving the clear idea about the table.
iii) Captions: It is also called the column heading, which gives a designation to the column. It is given as the top row. Under each column head, there may be subheads. In table-14.4 above, there are three captions: rank, name of country and production of wheat.
iv) Stubs: It is also called the row heading, which gives a designation to the row. It is given as the left column and that column is called the stub column.
v) Body of the Table: It is the most important part of the table. It contains the actual data. The body is arranged generally from left to right in rows and from top to bottom in columns.
vi) Unit of Measurement: The units of measurement of the figures in the data should always be given in the table. It can be given with the title if the same unit is used in the whole table. If different units are used for different columns, they should be given with the respective column headings; and if different units are used for different rows, they should be given with the respective row headings.
vii) Source: It is a brief statement indicating the source from where the data is taken. If more than one source, all of them should be written there. This will help the reader to check the figures and gather more information if required. It also helps in indicating the authenticity of data. Generally, source is written in the bottom of the table.
Various Kinds of Diagrams
There are various kinds of diagrams in common use. Amongst them the important ones are the following:
1. Geometric diagram
2. Frequency diagram
3. Arithmetic line graph
Geometric Diagram: Bardiagram and pie diagram come in the category of geometric diagram for the presentation of data. The bar diagrams are of three types- simple, multiple and component bar diagrams.
i) Bar Diagram
Simple Bar Diagram: Bardiagram comprises a group of Equi-spaced and equi-width rectangular bars for each class or category of data. The height or length of the bar reads the magnitude of data.
Multiple Bar Diagram: Multiple bar diagrams are used for comparing two or more sets of data, for example, import and export for different years, marks obtained in different subjects in different classes, etc.
Component Bar Diagram: Component bar diagrams or charts also called sub-diagrams are very useful in comparing the sizes of different component parts and also for throwing light on the relationship among these integral parts.
ii) Pie Diagram
A pie diagram is also a component diagram, but unlike a component bar diagram, a circle whose area is proportionally divided among the components it represents. It is also called a pie chart. The circle is divided into as many parts as there are components by drawing straight lines from the centre to the circumference. Pie charts usually are not drawn with absolute values of a category. The values of each category are first
expressed as a percentage of the total value of all the categories.
It may be interesting to note that data represented by a component^bar diagram can also be represented equally well by a pie chart, the only requirement being that absolute values of the components have to be converted into percentages before they can be used for a pie diagram.
Graphical Presentation
Data in the form of grouped frequency distributions are generally represented by frequency diagrams like histogram, frequency polygon, frequency curve and ogive.
a) Histogram: A histogram is a two-dimensional diagram. It is a set of rectangles with bases as the intervals between class boundaries (along X- axis) and with areas proportional to the class frequency. If the class intervals are of equal width, which they generally are, the area of the rectangles are proportional to their respective frequencies. However, in some type of data, it is convenient, at times necessary, to use varying width of class intervals. The width in a histogram is as important as its height. We can have a bar diagram both for discrete and continuous variables, but histogram is drawn only for a continuous variable. Histogram also gives value of mode of the frequency distribution graphically.
b) Frequency Polygon: A frequency polygon is a plane bounded by straight lines, usually four or more lines. Frequency polygon is an alternative to histogram and is also derived from histogram itself. A frequency polygon can be fitted to a histogram for studying the shape of the curve. The simplest method of drawing a frequency polygon is to join the midpoints of the topside of the consecutive rectangles of the histogram.
c) Frequency Curve: The frequency curve is obtained by drawing a smooth freehand curve passing through the points of the frequency polygon as closely as possible. It may not necessarily pass through all the points of the frequency polygon but it passes through them as closely as possible.
d) Ogive: Ogive is also called cumulative frequency curve. As there are two types of cumulative frequencies, for example less than type and more than type, accordingly there are two ogives for any grouped frequency distribution data. Here in place of simple frequencies as in the case of frequency polygon, cumulative frequencies are plotted along y-axis against class limits of the frequency distribution. For less than give the cumulative frequencies are plotted against the respective upper limits of the class intervals whereas for more than ogives the cumulative frequencies are plotted against the respective lower limits of the class interval. An interesting feature of the two ogives together is that their intersection point gives the median.