2. Data:
A set of values recorded on one or more observational
units i.e. Object, person etc
Types of data:
(A) Qualitative/ Quantitative data
(B) Discrete/ Continuous data
(C) Primary/ Secondary data
(D) Nominal/ Ordinal data
3. Qualitative data:
• also called as enumeration data .
• Represents a particular quality or attribute.
• There is no notion of magnitude or size of the
characteristic, as they can't be measured.
• Expressed as numbers without unit of
measurements . Eg: religion, Sex, Blood group etc.
Quantitative data:
• Also called as measurement data.
• These data have a magnitude.
• Can be expressed as number with or without unit of
measurement. Eg: Height in cm, Hb in gm%, BP in
mm of Hg, Weight in kg.
4. Discrete / Continuous data:
Discrete data: Here we always get a whole number.
Eg. Number of beds in hospital, Malaria cases .
Continuous data : it can take any value possible to
measure or possibility of getting fractions. Eg. Hb
level, Ht, Wt.
Quantitative data Qualitative data
Hb level in gm% Anemic or non anemic
Ht in cms Tall or short
BP in mm of Hg Hypo, normo or hypertensive
IQ scores Idiot, genius or normal
5. Primary/ Secondary data:
Primary data : Obtained directly from an individual , it
gives precise information .
Secondary data : Obtained from outside source ,Eg:
Data obtained from hospital records, Census.
Nominal/ Ordinal data:
Nominal data: the information or data fits into one of
the categories, but the categories cannot be ordered
one above another . E.g. Colour of eyes, Race, Sex.
Ordinal data: here the categories can be ordered,
but the space or class interval between two
categories may not be the same. E.g.. Ranking in
the class or exam
6. Collection of data
Collect data carefully and thoroughly.
Units of measurements should be clearly defined.
Record should be correct , complete, clear,
sufficiently concise and arranged in a manner that is
easy to comprehend.
Collected data should be
• Accurate (i.e. Measures true value of what is under study)
• Valid( i.e. Measures only what is supposed to measure)
• Precise(i.e. Gives adequate details of the measurement)
• Reliable(i.e. Should be dependable)
7. Presentation of data
Principles of presentation of data:
1. Data should be arranged in such a way that it will
arouse interest in reader.
2. The data should be made sufficiently concise
without losing important details.
3. The data should presented in simple form to
enable the reader to form quick impressions and to
draw some conclusion, directly or indirectly.
4. Should facilitate further statistical analysis .
5. It should define the problem and suggest its
solution.
8. Methods of presentation
of data
The first step in statistical analysis is to present
data in an easy way to be understood.
The two basic ways for data presentation are
Tabulation
Charts and diagram
9. Rules and guidelines for tabular
presentation
1. Table must be numbered
2. Brief and self explanatory title must be given to each
table.
3. The heading of columns and rows must be clear,
sufficient, concise and fully defined.
4. The data must be presented according to size of
importance, chronologically, alphabetically or
geographically
5. If data includes rate or proportion, mention the
denominator.
6. Table should not be too large.
7. Figures needing comparison should be placed as close
as possible.
10. Continued..
8. The classes should be fully defined, should not lead to
any ambiguity.
9. The classes should be exhaustive i.e. should include all
the given values.
10. The classes should be mutually exclusive and non
overlapping.
11. The classes should be of equal width or class interval
should be same
12. Open ended classes should be avoided as far as
possible.
13. The number of classes should be neither too large nor
too small.Can be 10-20 classes.
14. Formula for number of classes(K):
K=1+3.322 log10 N, where N is total frequency
11. Tabulation
Can be Simple or Complex depending upon the
number of measurements of single set or multiple
sets of items.
Simple table :
Title: Numbers of cases of various diseases in Nair hospital in 2009
Disease Cases
Malaria 1100
Acute GE 248
Leptospirosis 60
Dengue 100
Total 1308
12. Frequency distribution table with qualitative data:
Title: Cases of malaria in adults and children in the
months of June and July 2010 in Nair Hospital.
Jun-10 Jul-10
Type of
malaria Adult Child Adult Child Total
P.Vivax 54 9 136 23 222
P.Falciparu
m 11 0 80 13 104
Mixed
malaria 11 4 36 12 63
Total 76 13 225 43 389
13. Frequency distribution table with quantitative data:
Fasting blood glucose level in diabetics at the time of
diagnosis
Fasting
glucose level
No of diabetics
Male Female Total
120-129 8 4 12
130-139 4 4 8
140-149 6 4 10
150-159 5 5 10
160-169 9 6 15
170-179 9 9 18
180-189 3 2 5
44 34 78
14. Chart and diagram
Graphic presentations used to illustrate
and clarify information. Tables are
essential in presentation of scientific
data and diagrams are complementary
to summarize these tables in an easy,
attractive and simple way.
15. The diagram should be:
Simple
Easy to understand
Save a lot of words
Self explanatory
Has a clear title indicating its content
Fully labeled
The y axis (vertical) is usually used for
frequency
16. Various charts and diagrams
Bar Diagram
Histogram
Frequency polygon
Cumulative frequency curve
Scatter diagram
Line diagram
Pie diagram
17. Bar diagram
• Widely used, easy to prepare tool for comparing
categories of mutually exclusive discrete data.
• Different categories are indicated on one axis and
frequency of data in each category on another axis.
• Length of the bar indicate the magnitude of the frequency
of the character to be compared.
• Spacing between the various bar should be equal to half
of the width of the bar.
• 3 types of bar diagram:
Simple
Multiple or compound
Component or proportional
19. Multiple bar chart: Each observation has
more than one value, represented by a group
of bars. Percentage of males and females in
different countries, percentage of deaths from
heart diseases in old and young age, mode of
delivery (cesarean or vaginal) in different
female age groups.
21. Component bar chart : subdivision of a single bar to
indicate the composition of the total divided into sections
according to their relative proportion.
For example two communities are compared in their
proportion of energy obtained from various food stuff,
each bar represents energy intake by one community,
the height of the bar is 100, it is divided horizontally into
3 components (Protein, Fat and carbohydrate) of diet,
each component is represented by different color or
shape.
22. Component or proportional bar diagram
10
15
10
30
80
55
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Poor Community Rich Community
% of energy obtained Fats
% of energy obtained
Protein
% of energy obtained
Carbohdrate
23. Histogram:
It is very similar to the bar chart with the
difference that the rectangles or bars are
adherent (without gaps).
It is used for presenting class frequency table
(continuous data).
Each bar represents a class and its height
represents the frequency (number of cases),
its width represent the class interval.
25. Frequency Polygon
Derived from a histogram by connecting
the mid points of the tops of the rectangles
in the histogram.
The line connecting the centers of
histogram rectangles is called frequency
polygon.
We can draw polygon without rectangles
so we will get simpler form of line graph.
A special type of frequency polygon is the
Normal Distribution Curve.
27. Cumulative frequency diagram or O’give
Here the frequency of data in each category
represents the sum of data from the category and the
preceding categories.
Cumulative frequencies are plotted opposite the group
limits of the variable.
These points are joined by smooth free hand curve to
get a cumulative frequency diagram or Ogive.
29. Scatter/ dot diagram
Also called as Correlation diagram ,it is useful
to represent the relationship between two
numeric measurements, each observation
being represented by a point corresponding to
its value on each axis.
In negative correlation, the points will be
scattered in downward direction, meaning that
the relation between the two studied
measurements is controversial i.e. if one
measure increases the other decreases
While in positive correlation, the points will be
scattered in upward direction.
31. Line diagram:
It is diagram showing the relationship between two
numeric variables (as the scatter) but the points are
joined together to form a line (either broken line or
smooth curve. Used to show the trend of events
with the passage of time.
Changes in body temperature of a patient after use of antibiotic
36
36.5
37
37.5
38
38.5
39
39.5
1 2 2 4 5 6 7
time in hours
temperature
32. Pie diagram:
Consist of a circle whose area
represents the total frequency (100%)
which is divided into segments.
Each segment represents a
proportional composition of the total
frequency.
