When most people think of data, they probably think of a dry, technical analysis, without a lot of creativity or freedom. Quite to the contrary, data visualization encompasses choices of design, creative freedom, and also (perhaps most interestingly) elements of cognitive psychology, particularly related to the science of visual perception and information processing.
If you read any good text on dataviz, like Tufte, Few, or Cairo, you will, at some point, come across a discussion of the cognitive aspects of data visualization (the latter two devoting entire chapters to this topic). This will likely include a discussion of the most elemental ways to encode information visually, and their respective accuracies when quantity is interpreted from them, usually referencing the work of Cleveland & McGill [PDF].
Mulling over the veracity of my brief mention of the visual ways of encoding quantity in my recent talk, and also recently re-reading Nathan Yau's discussion of the aforementioned paper, I got to thinking about just how different the accuracy of interpretation between the different encodings might be.
I am not a psychologist or qualitative researcher, but given the above quickly put together a simple test of 7 questions in Google Docs, to examine the accuracy of interpreting proportional quantities when encoded visually; and I humbly request the favour of your participation. If there are enough responses I will put together what analysis is possible in a future post (using the appropriate visualization techniques, of course).
Apologies in advance for the grade-school wording of the questions, but I wanted to be as clear as possible to ensure consistency in the results. Thanks so much in advance for contributing! Click below for the quiz:
EDIT: The quiz will now be up indefinitely on this page.