Presenting data in a report without losing the reader

Data presentation is one of the few areas where marking schemes are explicit and students still lose marks routinely. The criteria usually say that figures must be labelled, numbered, referred to in the text and capable of being understood on their own. Most student reports fail at least two of those.

Every figure stands alone

A reader should be able to understand a chart from its caption, axis labels and legend alone, without hunting through the surrounding paragraphs. That means a caption describing what the figure shows rather than naming it, axes labelled with units, and a legend that does not rely on colour alone.

• Number every table and figure, and refer to each by number in the text
• Caption above tables, below figures, following your style guide
• Label axes with units, and state the sample size
• Never present a chart you do not discuss in the body
• Give the source for any data you did not collect yourself

Choose the form for the comparison

The chart type should follow from what you want the reader to see. Change over time is a line. Comparison between categories is a bar. Relationship between two variables is a scatter. Composition is awkward in every form, and pie charts stop being readable past about four slices.

If the chart needs a paragraph to explain what it shows, the chart is the wrong one.

Tables are not a dumping ground

A table with thirty rows and twelve columns is raw data, and raw data belongs in an appendix. What goes in the body is the summary that supports the point you are making. Round consistently, align numbers on the decimal point, and never present more precision than your measurement justifies.