types of data and methods of data collection and presentation
variables on a particular point of time or over different points of time.
cross-section data
Data collected on a single point of time over different sections.
time series data
data collected over a period of time.
Data may be quantitative or qualitative in nature. Data of quantitative nature are technically called
variables whereas data of qualitative nature are called attributes. If a variable can take any
value within its range, then it is called a continuous variable otherwise it is
called a discrete variable.
Depending on the type of collection, data may be of two types
Primary data
collected for a specific purpose directly from the field of enquiry and hence they are original in nature.
data collected by someone but used by another or collected for one purpose and used for another are called secondary data.
data are presented by the means of
i) Tables
ii) Charts and Diagrams.
Tabulation of data may be defined as the logical and systematic organisation of statistical data in rows and columns.
ADVANTAGES
simplify the presentation.
quick comparison.
errors and emissions could be readily detected.
avoidance of repetition of explanatory terms.
A table constructed for presenting the data has the following parts
1) Title: This is brief description of the contents and is shown on the top of
the table.
2) Stub: The extreme left part of a table is called Stub. Here the descriptions
of the rows are shown.
3) Caption and Box Head: The upper part of the table, which shows the
description of columns and sub columns, is called Caption. The row of the
upper part, including caption, units of measurement and column number,
if any, is called box-head.
4) Body: This part of the table shows the figures.
5) Footnote: In this part we show the source of data and explanations, if any.
Charts and Diagrams for Ungrouped Data
quickly.
A chart, can clarify complex problems and reveal the hidden facts.
unlike tables do not show details of data and require much time to construct.
The common types of charts and diagrams are,
1) Line diagrams.
2) Bar diagrams.
3) Pie diagrams.
4) Pictogram .
Line diagrams are the most common methods of presenting statistical data. Data presentation in the form of line diagrams are mostly used in business and commerce. Mostly, the time series data are represented by line diagrams. In a line diagram, data are shown by means of a curve or a
straight line. The straight line or the curve reveals the relationship between two variables. Two straight lines, one horizontal and another vertical (known as the X axis and Y axis, respectively), are drawn on the graph paper, which intersect at a point called origin. The given data are
represented as points on the graph paper. The locus of all such points joined either by curves or by pieces of straight lines gives the line diagram.
Two types of line diagrams are used, natural scale and ratio scale. In the
natural scale equal distances represent equal amounts of change. But in
ratio scale equal distances represent equal ratios.
Bar Diagrams: Bar diagram consists a group of equally spaced
rectangular bars, one for each category (or class) of given statistical data.
The rectangular bars are differentiated by different shades or colors. The
bars starting from a common baseline must be of equal width and their
length represents the values of statistical data. Bar diagrams may be of two
types: vertical and horizontal. For each of these types, we have again
grouped bar diagram, subdivided bar diagram, paired bar diagram etc.
Grouped bar diagrams are used to show the comparison of two or more
sets of related statistical data, while subdivided or component bar
diagrams are used for comparing the sizes of the different component parts
among themselves. The paired bar diagram consists of several pairs of
horizontal bars.
Pie diagrams: A pie diagram is a circle whose area is divided
proportionately among the different components by straight lines drawn
from the center to the circumference. When statistical data are given for a
number of categories and we are interested in their comparison in a
manner that reveals the contribution of each category to the total, pie
diagrams are very useful in effectively displaying the data.
In a pie diagram, it is necessary to express the value of each category as a
percentage of the total.
Since the circle represents the total and to
represent each category in that circle, we have to multiply the percentage
of each category by 3.6 degrees, so that sum of each category becomes
360 degrees.
Pictogram: This type of data presentation consists of rows of pictures or
symbols of equal size. Each picture or symbol represents a definite
numerical value. Pictograms help to present data to illiterate people or to
children.
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