Viewers of graphs, beware! Data visualization has been around for a very long time, but it has become ubiquitous since the onset of Big Data. Now, the Heap Data Blog warns us to pay closer attention in, “How to Lie with Data Visualization.” Illustrating his explanation with clear examples, writer Ravi Parikh outlines three common ways a graphic can be manipulated to present a picture that actually contradicts the data used to build it. The first is the truncated Y-axis. Parikh writes:
“One of the easiest ways to misrepresent your data is by messing with the y-axis of a bar graph, line graph, or scatter plot. In most cases, the y-axis ranges from 0 to a maximum value that encompasses the range of the data. However, sometimes we change the range to better highlight the differences. Taken to an extreme, this technique can make differences in data seem much larger than they are.”
The example here presents two charts on rising interest rates. On the first, the Y-axis ranges from 3.140% to 3.154% — a narrow range that makes the rise from 2008 to 2012 look quite dramatic. However, on the next chart the rise seems nigh non-existent; this one presents a more relevant span of 0.00% to 3.50% on the Y-axis.
Continue reading “Stephen E. Arnold: Using Real Data to Mislead”