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

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

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

 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

 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

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

# Year Figure 8.1. Trends in HIV prevalence among pregnant women in Country X, years 1 – 10 Example: Scale Line Graph

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

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

Example: Bar Chart Figure 8.2. Differences in HIV prevalence among various high-risk groups, Country X, year 1. #1-8-13

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

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

Example: Histogram # Figure 8.4. Children living with HIV, District X, 2002

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

# Example: Pie Chart Figure 8.5. Projected annual expenditure requirements for HIV/AIDS care and support by 2005, by region

Tables # 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.

# 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 <15 yearsTotal Total

In Summary v Data can be analysed by person, place or time. v Depending on your data, you can choose from a variety of chart and graph formats, including pie charts, histograms, tables, etc. v Using several simpler graphics is more effective than attempting to combine all of the information into one figure. #1-8-26