As software vendors flood us with flashy dashboards and widgets for our BI projects, some of which clearly obscure information more than they illuminate, I started hunting for research documenting which methods of charting are the most effective. Naomi B. Robbins "Creating More Effective Graphs" presentation fits the bill (turns out the presentation is based on her book of the same name: Creating More Effective Graphs). Good stuff and exactly what I needed. I bulleted out some of the key points below but the document itself is only eight pages and a very easy read. Link to the presentation is at the end of this post. (Strangely, Robbins doesn't recommend my personal favorite: The Radar Chart.)
- One graph is considered more effective than another if it's quantitative information can be decoded more quickly or more easily by most observers.
- A table is often very effective for small data sets.
- Avoid putting extra dimensions in your charts. The pseudo three-dimensional charts are difficult to read. If you know categories and values for each category, a two-dimensional chart is clearer than a pseudo three-dimensional one.
- Data labels don’t help; they confuse the reader even more.
- It is difficult to determine trends from stacked bar charts unless we are looking at the bottom category since lengths without a common baseline are difficult to compare.
- Dot plots allow us to decode the data by making judgments of positions along the common horizontal scale. Experiments have shown that this is the most accurate of the elementary graphical tasks.
- We judge position along identical nonaligned scales almost as accurately as position along a common scale.
- Alphabetical order is rarely the most effective. Ordering by size is often better.
- Bar charts get cluttered more quickly than dot plots.
- Eliminate unnecessary clutter. Look at the graph and notice what you see first. The answer should be the data (or model) and not grid lines, long labels, or other graphical elements.
- Reduce clutter by: 1. showing axes labels in thousands, millions, or billions instead of including strings of zeros. 2. Label an axis as percent or dollars rather than including a percent sign or dollar symbol at each tick mark label.
The original presentation on Creating More Effective Graphs can be found here.