The goal of this chapter is to help you understand how optimally to present data. The chapter draws heavily on three sources to which we refer readers for more details. For the presentation of data in the form of tables, Andrew Ehrenberg's A Primer in Data Reduction (2007) contains much good sound advice. For the use of figures, William Cleveland's The Elements of Graphing Data (1994) is a style guide that is required reading for anyone considering using a graph, from the most junior undergraduate to the most experienced researcher. Good advice is also available in the works of Tufte (2001) as well as in the sixth edition of the APA Manual (American Psychological Association, 2009).

Tables and figures allow large amounts of material to be presented concisely. Well presented, they often enable readers to understand at a glance patterns of data and exceptions that would be obscured if presented in the text. Tables and figures are more expensive for journals to produce than text, however, so if you plan to submit a paper for publication, you should present in this form only your most important sets of data. Do not duplicate data from one table or figure to another unless it is essential for comprehension. Extensive sets of data should be reported in appendices rather than in the body of the paper, or should be made available online with an appropriate note in the paper indicating the web address at which the data can be obtained.

The same principles that apply to the effective presentation of tables and figures also apply to effective scientific writing. The basic rule is to aim for a simple, direct presentation, without clutter.

Stylistic excesses like the moiré pattern graphics that appear on many histograms hinder rather than help, because they often direct attention away from the data. Edward Tufte (2001) uses the term chartjunk to refer to such unnecessary elements of graphs and has good advice on how to avoid it.

Care in preparing tables and figures helps you to understand your data. As you produce better versions, you explore your data and tease out meanings as well as choose how best to communicate the data. For this reason, tables and figures should be constructed first. Together with their captions, they should be able to communicate much of the information in the paper, without one's even having to read the text.