Biostatistics for medical students

1. Methods of Presentation of Data
Dr. Buddhi Krishna Shrestha
1st year Resident
Internal Medicine, NAMS

2. • The main sources for collection of medical
statistics are:
1. Experiments
2. Surveys
3. Records.

3. The statistical data obtained from the above
sources can be divided into two broad
categories:
1. Qualitative (or Discrete) Data
• No notion of magnitude or size of the characteristic or
attribute
• Only one variable
• Example: attacked, escaped, died, cured etc
2. Quantitative (or Continuous) Data
• The quantitative data have a magnitude.
• The characteristics is measured either on an interval or on a
ratio scale.
• There are two variables—the characteristics and the
frequency.
• Example: Height, weight, blood pressure etc

4. Principles of Presentation of Data
• Data should be arranged in such a way that it sparks interest in
reader
• Data should be made sufficiently concise without losing
important details
• Data should be presented in simple form to enable the reader
to form quick impressions and to draw some conclusion,
directly or indirectly.

5. • Should facilitate further statistical analysis
• Should define the problem and suggest its solution

6. METHODS OF PRESENTATION
• The first step in statistical analysis is to present the data in an
easy way to be understood.
• There are two main methods of presenting frequencies of a
variable character or a variable.
1.Tabulation
2.Drawing

7. 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. Figures needing comparison should be placed as close as possible

9. Tabulation
• Tabulation are devices for presenting data
from a mass of statistical data.
• Preparation of frequency distribution table is
the first requirement.
• Can be simple or complex depending upon the
number of measurements of single set or
multiple sets of items

10. Simple table
Diseases Cases
Hypertension 25000
Diabetes Mellitus 38000
Cancer 2000
Total 65000
Number of Cases of Non Communicable
diseases in XYZ Hospital in 2019

11. Frequency Distribution Table with
Qualitative Data
Cases of COVID-19 in adults and children in the
months of July and August 2020 in XYZ Hospital

12. Frequency Distribution Table with
Quantitative Data
Systolic Blood Pressure Level in Hypertensive Patients at the
diagnosis

13. • After classwise or groupwise tabulation, the
frequencies of a characteristic can be presented by
two kinds of drawings: Graphs and diagrams.
• Presentation of quantitative, continuous or
measured data is through graphs
• Presentation of qualitative, discrete or counted data
is through diagrams.

14.  Presentation of quantitative, continuous or
measured data is through graphs.
 The common graphs in use are:
•Histogram
•Frequency polygon
•Frequency curve
•Line chart or graph
•Cumulative frequency diagram
•Scatter or dot diagram.

15. Presentation of qualitative, discrete or
counted data is through diagrams.
The common diagrams in use are:
•Bar diagram
•Pie or sector diagram
•Pictogram or picture diagram
•Map diagram or spot map.

16. • Used for Qualitative, Continuous, Variables
• It is used to present variables which have no gaps eg.
age, weight, height, blood pressure, blood sugar etc.
• It consist of a series of blocks
• The class intervals are given along horizontal axis and
the frequency along the vertical axis
Histogram

17. Histogram showing
tuberculin reaction
in 206 persons,
never
vaccinated

18. • Frequency Polygon is an area diagram of frequency
distribution over a histogram
• It is a linear representation of a frequency table and
histogram, obtained by joining the mid points of the
histogram blocks
• Frequency is plotted at the central point of a group
Frequency Polygon

19. Frequency polygon showing tuberculin reaction in 206 persons
never vaccinated

21. • 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
Cumulative Frequency Diagram or O'give

23. • Also called the 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.
Scatter/ Dot diagram
Scatter/ Dot
diagram

24. Scatter diagram showing positive correlation

25. Scatter diagram showing negative correlation

26. • 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 a smooth
curve)
• Used to show the trend of events with the passage of time
Line Diagram

27. Time to achieve maximum antiplatelet effect with 75 mg
aspirin/day. It is maximum in first day then declines unless
taken next day again

28. 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

29. • Spacing between various bar should be
equal to half of the width of the bar
• 3 types of Bar diagram:
1. Simple Multiple
2. Compound Component
3. Proportional

30. Simple bar charts:

31. • 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 ( caserean
or vaginal) in different female age groups
Multiple Diagram

32. Multiple or Compound Diagram

33. • 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
Proportional or component bar
diagram

35. • 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
Pie diagram

36. Pie diagram showing alcohol drinking status of 391 alcohol
drinkingsubjects under medical and ocular history of
Bhaktapur (Nepal) vision impairmentand glaucoma study.

37. Pictogram or Picture Diagram
• It is a popular method to impress the
frequency of the occurrence of events to
common man such as attacks, deaths, number
operated, admitted, discharged, accidents,
etc. in a population.

38. AIDS in developing and industrially developed countries. The
burden of disease caused by HIV
infection is clear.

39. Map Diagram or Spot Map
• These maps are prepared to show geographical
distribution of frequencies of characteristic.

40. THANK YOU