بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم

2. Graphical Presentation Dr. Laila Mohamed Nofal Professor of Biostatistics High Institute of Public Health University of Alexandria

3. Graphical Presentation Graphical presentation is the use of a graph to show the distribution of data. Why ? • Attract the reader’s attention • A graph or diagram, provides an easily understood picture of the data. A suitable diagram is easier to grasp and leaves a more permanent impression of the main features of the data • To compare two or more distributions.

4. There are many varieties of graphs. The use of a particular type depends on: Type of data (quantitative continuous or discrete or qualitative) Type of table (simple or complex) Graphical Presentation

5. Line Graph = Trend Line • One quantitative variable & Time. • Time may be years, months, weeks, days, hours…) • No frequency distribution. • May be one or more quantitative variables bytime.

6. The Line Graph Example:

7. The Line Graph Figure (1) Crude birth rate of Country X 1997-2001

8. Figure (1) Crude birth rate of Country X 1997-2001

9. The Line Graph

10. Histogram • For quantitative continuous variables • S.F.D.T only

11. Example:

12. Example: Age in Years Figure (2): Distribution of patients by age in Hospital X, 2011

13. Frequency Polygon • Quantitative continuous variable • SFDT or Complex FDT

14. Frequency Polygon • SFDT • Points are joined by straight line

15. Frequency Polygon • Complex FDT • Points are joined by straight line

16. Distribution of a group of patients by age

17. Distribution of a group of patients by age

18. Example: Frequency Polygon

19. Figure (3): Distribution of patients by age and sex in Hospital X, 2012

20. Frequency Curve • Quantitative continuous variable • SFDT or Complex FDT • Points are joined by a smooth curve • The more the number of points (categories) the more smooth will be the curve

21. Distribution of malaria cases by age

22. Bar Graph • Qualitative or quantitative discrete variables • Simple or complex frequency table

23. Bar Graph • Simple frequency table

24. Bar Graph • Complex frequency table

25. Example

26. Bars should be of equal widths and inter bar spacing and differ only in height

27. Example

29. The Pie Chart This type of graph can be used with all types of variables in simple frequency distribution tables. The pie is divided into a number of sectors equal to the number of categories in the table so that each sector will represent one category from the table. The starting line for sub-division of the circle is usually taken as 12 o’clock radius. The sub-division of the pie is usually in a clockwise direction. The angle of the sector representing a particular category can be determined as follows: angle = Frequency of each category X 360 Total frequency

30. The Pie Chart Angle for single = 20 x360 = 100⁰ 72 Angle for married = 30 x360 = 150⁰ 72 Angle for widowed= 10 x360 = 50⁰ 72 Angle for divorced= 20 x360 = 60⁰ 72 Total = 100+150+50+60= 360⁰

31. The Pie Chart Figure (4): Distribution of patients by marital status in Hospital X, in the year 2012

32. Pie Chart Distribution of patients according to their blood group and sex

33. Pie Chart Distribution of patients according to their blood group and sex Male Female

34. Graphs Qualitative Data Quantitative Data SFDT Complex Complex SFDT Bar Chart Bar Chart Pie Chart Discrete Continuous Bar Chart Histogram Discrete Continuous Freq. Polygon Bar Chart Freq. Polygon