Let’s pretend you’re tracking whether friendly reminder messages bring in more responses to your survey.
Can you spot the fatal flaw?
Go check out the x-axis.
Where the heck are Days 5, 6, 7, 12, 13, 14, and 20?
(This is where you gasp.)
Yep, the analyst accidentally skipped a few labels along the x-axis. This is an innocent enough mistake. Most likely, there weren’t any responses to the survey on Days 5, 6, 7, 12, 13, 14, and 20. So the analyst was busy and forgot to manually insert “0’s” for those days in the data table.
This is what Stephanie Evergreen and I described in our Data Visualization Checklist: Axis labels are equidistant means that the spaces between axis intervals should be the same unit, even if every axis interval isn’t labeled.
Here’s what that graph should’ve looked like.
Can you spot the differences now?
The dotted line is the incorrect graph and the solid line is the correct graph.
Our analyst’s error means the readers saw an incorrectly shaped graph.
I can’t tell you how many times I’ve seen this same mistake in published research and evaluation reports. The analysts have accidentally skipped days, years, cohorts, and so on. Whoops!
The good news: What an easy fix. Just add new rows or columns to your data table, insert some 0’s, and voila! your graph will have equidistant axis labels.
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Coming to Denver for the American Evaluation Association’s annual conference?
- Grab one-on-one data visualization consulting at the Slide Clinic: Wednesday, October 15, 2014 from 8 – 9 pm.
- Attend the Data Visualization and Reporting Topical Interest Group’s meeting: Thursday, October 16, 2014 from 7:15 – 8:45 pm.
- Learn more about data visualization best practices from Stephanie Evergreen and I: Friday, October 17, 2014 from 11 – 11:45 am.
- Learn to produce slidedocs in lieu of dusty shelf reports: Friday, October 17, 2014 from 4:30 – 5:15 pm.
Or, contact me and we’ll grab coffee.