2.
“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.”
-Seligman
3.
Collection
of data
Organisatio
n of data
Presentation
of data
Analysis
of data
Interpretatio
n of data
Stage 1 Stage 2 Stage 3 Stage 4
Stage 5
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
sample method
Stage 2 Organisation of
data
Tally bars
Stage 3 Presentation of
data
Tables, graphs
and polygons,
histograms etc
Stage 4 Analysis of data Percentages
,Averages
Stage 5 Interpretation of
data
Magnitude of
percentages
5.
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
6.
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
7.
Scores(mid
points)
Frequency
5
15
25
35
45
2
5
7
10
4
Ascertainment of lower and upper
limits :
Get the difference between the first
and the second mid point .
Divide it by 2 to get the intervals and
then draw the histogram.
8.
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
interval
Marks No of
students
Adjustment
factor
Frequency
density
30-50
50-60
60-70
70-90
90-100
48
30
20
28
16
20/10=2
10/10=1
10/10=1
20/10=2
10/10=1
48/2=24
30/1=30
20/1=20
28/2=14
16/1=16
9.
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
10.
Class limits No of sareees
100-200
200-300
300-400
400-500
500-600
600-700
700-800
10
27
37
24
20
15
10
The total area excluded from the
histogram is equal to the area
included under frequency polygon
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