Purpose of Displaying Data The purpose of developing clearly understandable tables, charts and graphs is to allow you to: Analyse the data easily Effectively and quickly communicate information that might be complex #1-8-5

General Rules for Displaying Data Simpler is better. Graphs, tables and charts can be used together. Use clear descriptive titles and labels. Provide a brief description below each table or graph of what the display shows us. #1-8-7

Specific Rules: Line Graphs X-axis should be longer than Y-axis ALWAYS Start the Y-axis with zero Determine the range of values needed (i.e. 10 to 45?) Select an interval size #1-8-11

Example: Line Graph Figure 8.1. Trends in HIV Year Figure 8.1 illustrates the change in the percentage of HIV cases between 1991 and 2000. It is clear that there has been a steady decrease with the percentage decreasing from 29% to 11% during that period. The largest number of HIV cases was reported in 1992. #1-8-10

Bar Charts Uses differently coloured or patterned bars to represent different groups Y-axis represents how often something occurs X-axis may represent time or different groups etc. #1-8-12

Example: Bar Chart Figure 8.2. Differences in HIV Figure 8.2 shows the amount of HIV infection by the type of population. Prisoners had the highest occurrence of the disease with female sex workers following close behind. Refugees from other countries had the lowest incidence of HIV. #1-8-13

Specific Rules: Bar Charts Arrange categories that define bars in a natural order (for example by age). If natural order does not exist, define categories by name, such as grade or gender Make bars the same width. #1-8-14

Clustered Bar Charts Bars can be presented as clusters or groups. These are useful to compare values across categories. They are sometimes called stacked bar charts. #1-8-15

Example: Clustered Bar Chart Figure 8.3. HIV Rate by Site Figure 8.3 shows the amount of HIV reported at different sites. Site 2 had the highest incidence of HIV for 3 all years. All sites had fewer cases by Year 3 with Site 4 being the lowest. #1-8-16

Specific Rules: Clustered Bar Charts Show no more than three sub-bars within a group of bars. Use different colours or patterns to show different sub-groups for the variables being shown and include a Legend. #1-8-17

Pie Charts A circular (360 degree) graphic representation Compares categories to the total amount #1-8-20

Example: Pie Chart #1-8-21

Tables 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. #1-8-24

Adults and adolescents ≥ 15 years 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 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 10 545 000 5 000 550 000 7 086 800 948 200 8 035 000 #1-8-25

What Might You Put in a Graph? Students average marks by GRADE! #1-8-24

What Might You Put in a Graph? Students average marks AND how much homework they do by GRADE! Why doesn’t this graph work?????? #1-8-24

What Might You Put in a Graph? Students CURRENT marks AND their PREVIOUS marks…by GRADE! Why does this graph work?????? #1-8-24

Displaying Your Data Remember: Below or beside each graphic, you must write about 4 sentences to explain what the graph shows. #1-8-24