Avoid This Danger When Choosing Metrics

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I’m all about making data clear and easy-to-digest. But there is a danger in it. The clarity may cause you accept what the data seems to tell you. You may not linger. You may not reflect.

Writer Margaret J. Wheatley warns us that “without reflection, we go blindly on our way, creating more unintended consequences, and failing to achieve anything useful.”

Economist Charles Goodhart recognized this danger in the metrics we create to measure our progress. At first, a certain metric may seem like a good indicator of progress. If we want kids in an after-school track program to increase their endurance, we might measure how far they run at the beginning of the program and then again at the end.  Makes sense, right? We might then try to motivate students by offering them free running shorts if they increase their miles by a certain amount. But, that’s when students might start gaming the system. They can increase their miles not only by training hard and running farther over time but also by running very short distances at the start. This is the kind of unintended consequence that Goodhart warned us about. His law states: “When a measure becomes a target, it ceases to be a good measure.” 

The solution? First, reflection. Consider the potential unintended consequences of each of your metrics, particularly those tied to incentives. Second, use multiple metrics to provide a more balanced understanding of progress.  In our running example, in addition to the change in miles participants run, you might also measure resting heart rates at the beginning and end of the program, knowing that a lower resting heart rate generally indicates a higher level of cardiovascular fitness.

See other data tips in this series for more information on how to effectively visualize and make good use of your organization's data. 

Bar Chart Hack #4: Radial Charts

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Welcome to Episode 3 of “How to Hack a Bar Chart.” This time we consider two bar chart species that recast the regular bar chart in circular form. They may be eye-catching but be careful how you use them.

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Radial Column Chart: (aka Circular Column Graph or Star Graph). As you can see in the example above, the bars on this chart are plotted on a grid of concentric circles, each representing a value on a scale. Usually, the inner circles represent lower values and values increase as you move outward. Sometimes each bar is further divided using color to show subgroups within each category. Because we are better at assessing length along a common scale, this type of chart isn’t ideal if you want viewers to accurately compare the lengths of each bar. However, these charts are great at showing cyclical patterns. Florence Nightingale used this type of chart (which she called a polar area chart) to show a cyclical pattern in the number and causes of death in the Crimean war.

This work is in the public domain in its country of origin and other countries and areas where the copyright term is the author's life plus 70 years or less.


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Radial Bar Chart (aka Circular Bar Chart) is simply a bar chart in which the bars curve around a circle, like runners on a circular track. As you may recall, races on circular or oval running tracks include staggered starting lines so that runners on the outer (longer) tracks run the same distance as those on the inner (shorter) tracks. But the bars on a radial chart have the same starting line making it difficult to compare lengths. So skip the radial bar chart. Not worth the effort.

See other data tips in this series for more information on how to effectively visualize and make good use of your organization's data.