Unit 8: Presenting Data in Charts, Graphs and Tables #1-8-1.

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Unit 8: Presenting Data in Charts, Graphs and Tables #1-8-1 Slide 2 Warm Up Questions: Instructions v Take five minutes now to try the Unit 8 warm up questions in your manual. v Please do not compare answers with other participants. v Your answers will not be collected or graded. v We will review your answers at the end of the unit. #1-8-2 Slide 3 What You Will Learn v 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 Slide 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 Slide 5 Purpose of Displaying Data v 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 Slide 6 Types of Variables v 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 v Continuous variables are items that occur in numerical order. #1-8-6 Slide 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. Dont compare variables with different scales of magnitude. #1-8-7 General Rules for Displaying Data Slide 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 Slide 9 Scale Line Graph v Scale line graph: represents frequency distributions over time v Y-axis represents frequency. v X-axis represents time. #1-8-9 Slide 10 #1-8-10 Year Figure 8.1. Trends in HIV prevalence among pregnant women in Country X, years 1 10 Example: Scale Line Graph Slide 11 Specific Rules: Scale Line Graphs v Y-axis should be shorter than X-axis v Start the Y-axis with zero v Determine the range of values needed v Select an interval size #1-8-11 Slide 12 Bar Charts v Uses differently coloured or patterned bars to represent different classes v Y-axis represents frequency v X-axis may represent time or different classes #1-8-12 Slide 13 Example: Bar Chart Figure 8.2. Differences in HIV prevalence among various high-risk groups, Country X, year 1. #1-8-13 Slide 14 Specific Rules: Bar Charts v Arrange categories that define bars in a natural order (for example, age). v If natural order does not exist, define categories by name, such as country, sex or marital status. v Position the bars either vertically or horizontally. v Make bars the same width. v Length of bars should be proportional to the frequency of event. #1-8-14 Slide 15 Clustered Bar Charts v Bars can be presented as clusters of sub-groups in clustered bar charts. v These are useful to compare values across categories. v They are sometimes called stacked bar charts. #1-8-15 Slide 16 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 Example: Clustered Bar Chart Slide 17 Specific Rules: Clustered Bar Charts v Show no more than three sub-bars within a group of bars. v Leave a space between adjacent groups of bars. v Use different colours or patterns to show different sub-groups for the variables being shown. v Include a legend that interprets the different colours and patterns. #1-8-17 Slide 18 Histograms v A representation of a frequency distribution by means of rectangles v Width of bars represents class intervals and height represents corresponding frequency #1-8-18 Slide 19 Example: Histogram #1-8-19 Figure 8.4. Children living with HIV, District X, 2002 Slide 20 Pie Charts v A circular (360 degree) graphic representation v Compares subclasses or categories to the whole class or category using differently coloured or patterned segments #1-8-20 Slide 21 #1-8-21 Example: Pie Chart Figure 8.5. Projected annual expenditure requirements for HIV/AIDS care and support by 2005, by region Slide 22 Area Maps v A graph used to plot variables by geographic locations #1-8-22 Slide 23 Example: Area Map Figure 8.6. HIV Prevalence in Adults in Africa, end 2003 #1-8-23 Source: UNAIDS, 2003 Slide 24 Tables #1-8-24 v A rectangular arrangement of data in which the data are positioned in rows and columns. v Each row and column should be labelled. v Rows and columns with totals should be shown in the last row or in the right-hand column. Slide 25 #1-8-25 Table 8.1. Adults and children with HIV/AIDS by region in Country Y, end year X Example: Table RegionAdults and adolescents 15 years Children