Definition of Characteristics

Features of graphical excellence4–7 (Features that facilitate the depiction of detailed or complex data relationships)

a. Paired data — Data are paired when 2 or more measurements are made in the same subject — either one parameter measured in the same subject at multiple times, or more than one variable measured simultaneously. A graph was given credit for pairing when it portrayed the inherent linkage of these measurements or variables.

b. Symbolic dimensionality — The use of varying symbols (e.g., letters, numbers, shapes) to depict an additional characteristic of the population beyond the comparison that the basic graph is intended to make.

c. Small multiples — The presentation of an array of small graphs, each of the same type, designed to convey information about each individual cell but, more importantly, the relationship of each cell to the entire array. Small multiples can be used when symbolic dimensionality is impractical.

Internal graph errors — contradictions within the graph. For example, axis values that do not correspond to the actual distance along the axis.

Visual clarity — graphical depiction that does not obfuscate the interpretation of data points, confidence intervals, axes or labels.

Nonstandard graphing conventions without explanation — elements that have widely accepted definitions (e.g., the horizontal lines of a box-and-whisker plot) are given alternate meanings without any indication in the graph legend that this has occurred.

External graph error — any discrepancy between the data presented in the text or tables of the advertisement and the values depicted in the graphic.

Redundancy within the graph — repetition of information within the graphic and its legend, e.g., the clear depiction of a parameter's value by an appropriately demarcated axis and the labeling of the parameter's value with its numerical value as well.

Redundancy of the graphic with text/table — declared when the graphic presented no unique information beyond that contained in text, tables, or other graphics.

“Chartjunk”— extraneous decoration that creates “visual noise” and distracts from the informative elements of the graph.8

Data density index — a statistic that measures the amount of information conveyed per square centimeter of graph.2,5 The numerator is the number of pieces of information illustrated in the graphic. The denominator is the number of square centimeters that the graph occupies including axes and axis labels, but not titles or legends.