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# Unit 8 presenting data in charts, graphs and tables

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### Unit 8 presenting data in charts, graphs and tables

1. 1. Unit 8: Presenting Data in Charts, Graphs and Tables #1-8-1
2. 2. Warm Up Questions: Instructions  Take five minutes now to try the Unit 8 warm up questions in your manual.  Please do not compare answers with other participants.  Your answers will not be collected or graded.  We will review your answers at the end of the unit. #1-8-2
3. 3. What You Will Learn  By the end of this unit you should be able to:  list the variables for analysing surveillance data  identify the types of charts and graphs and when the use of each is appropriate #1-8-3
4. 4.  Person: Who develops a disease (for example, by age group or sex)? Are the distributions changing over time?  Place: Where are cases occurring? Is the geographical distribution changing over time?  Time: Is the number of reported cases changing over time? #1-8-4 Analysing Surveillance Data
5. 5. Purpose of Displaying Data  The purpose of developing clearly understandable tables, charts and graphs is to facilitate:  analysis of data  interpretation of data  effective, rapid communication on complex issues and situations #1-8-5
6. 6. Types of Variables  Categorical variables refer to items that can be grouped into categories.  Ordinal variables are those that have a natural order.  Nominal variables represent discrete categories without a natural order.  Dichotomous variables have only two categories  Continuous variables are items that occur in numerical order. #1-8-6
7. 7.  Simpler is better.  Graphs, tables and charts can be used together.  Use clear descriptive titles and labels.  Provide a narrative description of the highlights.  Don’t compare variables with different scales of magnitude. #1-8-7 General Rules for Displaying Data
8. 8.  A diagram shown as a series of one or more points, lines, line segments, curves or areas  Represents variation of a variable in comparison with that of one or more other variables #1-8-8 Graphs
9. 9. Scale Line Graph  Scale line graph: represents frequency distributions over time  Y-axis represents frequency.  X-axis represents time. #1-8-9
10. 10. Example: Scale Line Graph Figure 8.1. Trends in HIV prevalence among pregnant women in Country X, years 1 – 10 40 30 20 10 0 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 % Source: STD/AIDS Control Programme, Uganda (2001) HIV/AIDS Surveillance Report #1-8-10 Year
11. 11. Specific Rules: Scale Line Graphs  Y-axis should be shorter than X-axis  Start the Y-axis with zero  Determine the range of values needed  Select an interval size #1-8-11
12. 12. Bar Charts  Uses differently coloured or patterned bars to represent different classes  Y-axis represents frequency  X-axis may represent time or different classes #1-8-12
13. 13. Example: Bar Chart Figure 8.2. Differences in HIV prevalence among various high-risk groups, Country X, year 1. 30 25 20 15 10 5 0 Female sex workers Men who have sex with men Injecting drug users Prisoners Refugees Population % HIV prevalence #1-8-13
14. 14. Specific Rules: Bar Charts  Arrange categories that define bars in a natural order (for example, age).  If natural order does not exist, define categories by name, such as country, sex or marital status.  Position the bars either vertically or horizontally.  Make bars the same width.  Length of bars should be proportional to the frequency of event. #1-8-14
15. 15. Clustered Bar Charts  Bars can be presented as clusters of sub-groups in clustered bar charts.  These are useful to compare values across categories.  They are sometimes called stacked bar charts. #1-8-15
16. 16. Example: Clustered Bar Chart Figure 8.3. HIV prevalence rate among pregnant 15- to 19-year-olds at 4 clinic sites, City X, Country Y, years 1 – 3 #1-8-16 35 30 25 20 15 10 5 0 Site 1 Site 2 Site 3 Site 4 Clinic Year 1 Year 2 Year 3 HIV prevalence (%) Source: Ministry of Health, Count ry Y. Annual AIDS Surveillance Report, year 3.
17. 17. Specific Rules: Clustered Bar Charts  Show no more than three sub-bars within a group of bars.  Leave a space between adjacent groups of bars.  Use different colours or patterns to show different sub-groups for the variables being shown.  Include a legend that interprets the different colours and patterns. #1-8-17
18. 18. Histograms  A representation of a frequency distribution by means of rectangles  Width of bars represents class intervals and height represents corresponding frequency #1-8-18
19. 19. Example: Histogram #1-8-19 Figure 7.3. Children Living with HIV, Figure 8.4. Children living with HIV, District X, 2002 District X, 2002 160 140 120 100 80 60 40 20 0 <1 1 2 3 4 5 - 9 10 - 13
20. 20. Pie Charts  A circular (360 degree) graphic representation  Compares subclasses or categories to the whole class or category using differently coloured or patterned segments #1-8-20
21. 21. #1-8-21 Example: Pie Chart Figure 8.5. Projected annual expenditure requirements for HIV/AIDS care and support by 2005, by region
22. 22. Area Maps  A graph used to plot variables by geographic locations #1-8-22
23. 23. Example: Area Map Figure 8.6. HIV Prevalence in Adults in Africa, end 2003 #1-8-23 Source: UNAIDS, 2003
24. 24. Tables #1-8-24  A rectangular arrangement of data in which the data are positioned in rows and columns.  Each row and column should be labelled.  Rows and columns with totals should be shown in the last row or in the right-hand column.
25. 25. #1-8-25 Example: Table Table 8.1. Adults and children with HIV/AIDS by region in Country Y, end year X Region Adults and adolescents ≥ 15 years Children <15 years Total 1 14 800 200 15 000 2 400 000 20 000 420 000 3 997 000 3 000 1 000 000 4 985 000 15 000 1 000 000 5 1 460 000 40 000 1 500 000 6 465 000 35 000 500 000 7 940 000 10 000 950 000 8 380 000 220 000 600 000 9 900 000 600 000 1 500 000 10 545 000 5 000 550 000 Total 7 086 800 948 200 8 035 000
26. 26. In Summary  Surveillance data can be analysed by person, place or time.  Depending on your data, you can choose from a variety of chart and graph formats, including pie charts, histograms, tables, etc.  Using several simpler graphics is more effective than attempting to combine all of the information into one figure. #1-8-26
27. 27. Warm Up Review  Take a few minutes now to look back at your answers to the warm up questions at the beginning of the unit.  Make any changes you want to.  We will discuss the questions and answers in a few minutes. #1-8-27
28. 28. Answers to Warm Up Questions 1. List two demographic variables by which surveillance data can be analysed. #1-8-28
29. 29. Answers to Warm Up Questions, Cont. 1. List two demographic variables by which surveillance data can be analysed. Age, sex, marital status, etc. #1-8-29
30. 30. Answers to Warm Up Questions, Cont. 2. True or false? Compiling all the data into one comprehensive chart or graph is more effective than including many simpler diagrams. #1-8-30
31. 31. Answers to Warm Up Questions, Cont. 2. True or false? Compiling all the data into one comprehensive chart or graph is more effective than including many simpler diagrams. False #1-8-31
32. 32. Answers to Warm Up Questions, Cont. 3. Which of the following cannot be extracted from public health surveillance data: a. changes over time b. changes by geographic distribution c. differences according to subject’s sex d. none of the above #1-8-32
33. 33. Answers to Warm Up Questions, Cont. 3. Which of the following can not be extracted from public health surveillance data: a. changes over time b. changes by geographic distribution c. differences according to subject’s sex d. none of the above #1-8-33
34. 34. Answers to Warm Up Questions, Cont. 4. Match the type of chart/graph with its example. #1-8-34
35. 35. Answers to Warm Up Questions, Cont. 4. Match the type of chart/graph with its example: scale line graph: d area map: c pie chart: a histogram: b #1-8-35
36. 36. Small Group Discussion: Instructions  Get into small groups to discuss these questions.  Choose a speaker for your group who will report back to the class. #1-8-36
37. 37. Small Group Reports  Select one member from your group to present your answers.  Discuss with the rest of the class. #1-8-37
38. 38. Case Study: Instructions  Try this case study individually.  We’ll discuss the answers in class. #1-8-38
39. 39. Case Study Review  Follow along as we go over the case study in class.  Discuss your answers with the rest of the class. #1-8-39
40. 40. Questions, Process Check  Do you have any questions on the information we just covered?  Are you happy with how we worked on Unit 8?  Do you want to try something different that will help the group? #1-8-40