Another way to show the information in a divergent bar chart, like the one I posted a few days ago, is in a split bar chart. Datawrapper staff wrote a blog post not recommending divergent bar charts, so they only offer a split bar chart.
I put together this split bar chart to get a better idea of what the Maryland Comprehensive Assessment Program (MCAP) results would look like displayed in this manner. In addition to the five score levels, I added a percent proficient column which is level 4 and level 5 added together. Percent proficient is reported in the official data chart and shown in the official column charts developed by the Maryland State Department of Education for the Maryland Report Card. The percent proficient is shown in green on the right of the centerline in my divergent bar chart.
I’m not sold that a split bar chart is always superior to a divergent bar chart. Especially when the data has categories that are distinctly good or bad and no awkward middle neutral category. However, I like the split bar chart. I especially like that it can be easily sorted by percent proficient, which includes levels 4 and 5. For this data, the percent proficient is more important than the percentage of students at each level.
I find it interesting that the percent proficient ranges from nearly 70% to less than 20%. With such a large gap, it is likely that there are methods that can be learned from the higher-performing counties to increase scores (and hopefully ultimately learning) in the lower-performing counties.
Notes About the Data
- Values listed as 5.0% are acutally less than or equal to 5.0%. I am not sure if there is a way to show uncertain values in Datawrapper bar charts. In education data with small populations is often repressed. I could probably back into some of these numbers but I have not for this chart as the goal is to look at the data visualization.