Discrete Versus Solid

It is common in infographics for quantities to be represented by stacks of discrete blocks. For example, a magazine illustration showing automobile production in different countries might use stacks of blocks with each block representing a thousand cars. This is unlike what is done to represent quantity in the charts used by statisticians, or for quantitative glyphs used in maps. In these cases, solid bars or solid area glyphs such as circles are commonly used to represent quantity. This raises the question of whether breaking bars, area, or volume glyphs into discrete blocks can improve the rapid estimation of quantity. We report on a study where participants compared quantities represented using bar, area, and volume glyphs in both solid and discrete variants. The discrete variants used up to 4, 4 × 4, and 4 × 4 × 4 blocks or 10, 10 × 10, and 10 × 10 × 10 blocks for bar, area, and volume, respectively. The results show that people are significantly more accurate in estimating quantities using the discrete versions, but they take somewhat longer. For both areas and volumes, the accuracy gains were considerable.