EXPLORING AND PRESENTING DATA
Exploring and presenting individual variables
To show specific values The simplest way of summarising data for individual variables so that specific values can be read is to use a table (frequency distribution). For descriptive data, the table sum-marises the number of cases (frequency) in each category. For variables where there are likely to be a large number of categories (or values for quantifiable data), you will need to group the data into categories that reflect your research question(s) and objectives.
To show highest and lowest values Tables attach no visual significance to highest or lowest values unless emphasised by alternative fonts. Diagrams can provide visual clues, although both categorical and quan-tifiable data may need grouping (Henry, 1995). For categorical and discrete data, bar charts and pictograms are both suitable. Generally, bar charts provide a more accurate representation and should be used for research reports, whereas pictograms convey a general impression and can be used to gain an audience’s attention. In a bar chart, the height or length of each bar represents the frequency of occurrence. Bars are separated by gaps, usually half the width of the bars. Bar charts where the bars are vertical (as in Figure 12.2) are sometimes called column charts. This bar chart emphasises that the European Union Member State with the highest per capita amount of municipal waste in 2003 was Ireland, whilst Poland had the lowest per capita amount of municipal waste. To emphasise the relative values represented by each of the bars in a bar chart, the bars may be reordered in either descending or ascending order of the frequency of occurrence represented by each bar (Figure 12.3). Most researchers use a histogram to show highest and lowest values for continuous data. Prior to being drawn, data will often need to be grouped into class intervals. In a histogram, the area of each bar represents the frequency of occurrence and the con-tinuous nature of the data is emphasised by the absence of gaps between the bars. For
Kilograms of waste per person
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Municipal waste: collected, land-filled and incinerated in 2003 by European Union member states Source: Eurostat (2005) European Regional and Urban Statistics
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eta 6f c’ .9* K‘6 6 6 PJ – c e 9 eq’ ecs “b. 6,0 ,,ocs 4,6 e 6(1,, – Figure 12.2 Bar chart Source: Adapted from Eurostat (2005) European Regional and Urban Statistics – Reference Guide, 2005 Edition. © European Communities, 2005. Reproduced with permission.
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