Edward Tufte's Small Multiples Print

Edward Tufte, expert in information design, and author of Beautiful Evidence, Visual Explanations, Envisioning Information, and The Visual Display of Quantitative Information describes a technique called "Small Multiples."  Let's use this technique to inspect data generated with a cytokine bead array run on a flow cytometer.

Complex life-science experiments can yield challenging data sets. In one case, researchers at David Wagner’s laboratory at the Webb-Waring Center, University of Colorado School of Medicine, in Denver, Colorado used a Bender MedSystems human cytokine bead array to study differences in cytokine production in 19 donors (7 healthy controls, 12 with Type 1 Diabetes (T1D)). Four different experimental conditions—unstimulated, stimulated with anti-CD3, stimulated with anti-CD40, and stimulated with the combination of anti-CD3 and anti-CD40—were considered.

We can use the following row of scatterplots to inspect the summarized data representing unstimulated production for all 10 cytokines.

Now, let's include more data in our analysis.

Including results for all 4 stimulation environments yields the following scatterplot array, which is what Tufte would call a "small multiples" presentation.

According to Tufte, small multiples:
• reveal repetition and change, pattern and surprise—the defining elements in the idea of information;
• directly depict comparisons, the essence of statistical thinking;
• create visual lists of objects and activities, nouns and verbs, helping viewers to analyze, compare, differentiate and decide; and
• amplify, intensify, and reinforce the meaning of images.

In this case, the scatterplot array provides a concise mental model of experimental results, providing a basis for informed conversation among all members of the research team.