“Statistics is the science that deals with the
method of collecting, classifying,
presenting, comparing ,and interpreting
numerical data collected to throw some
light on any sphere of enquiry.”
n of data
n of data
Stage 1 Stage 2 Stage 3 Stage 4
Each stage of statistical study involves the use
of certain techniques or methods
Stages Statistical study Statistical tools
Stage 1 Collection of data Census or
Stage 2 Organisation of
Stage 3 Presentation of
Stage 4 Analysis of data Percentages
Stage 5 Interpretation of
Graphic representation gives a visual effect.
Its used in research work for visual
presentation and analysis of data. The
graphic method enables us to present data in
a simple, clear and effective manner
There are many varieties of graphs .Broadly
graphs can be divided into two parts:
a) Graphs of frequency distribution
b) Graphs of time series
Histogram is joining rectangular diagram of a continuous
series in which each rectangle represents the class interval
with the frequency .It is a two-dimensional diagram and also
called frequency histogram.
Cases of constructing a hisogram
i. Histogram of equal class interval
ii. Histogram when mid points are give
iii. Histogram when unequal class intervals
Ascertainment of lower and upper
Get the difference between the first
and the second mid point .
Divide it by 2 to get the intervals and
then draw the histogram.
Before presenting the data in the form of
graphs and frequencies , unequal class
intervals are adjusted.
Adjustment factor=class interval of
concerned class divided by lowest class
Marks No of
Polygon is another form of diagrammatic presentation
of data .
It is formed by joining all the mid points of the tops of
all rectangles .however they can be formed even
without constructing a histogram.
Frequency polygons can be drawn in two ways:
i. With a histogram
ii. Without a histogram
Class limits No of sareees
The total area excluded from the
histogram is equal to the area
included under frequency polygon