180 Days of Ideas for Discussion in Math Class.
(as of 9July2014, we're in overtime!)
Since they tell you what the numbers mean I don't think this really counts as an error, although I'd probably call the horizontal axis "intervals" or something to reflect this. I could be missing some other error you have in mind too.That's not to say that it's not a tremendously stupid graph, however. Such a nonstandard and misleading way of representing the intervals is sure to cause a lot of confusion.
Oh dear, I just noticed that there is a point at (10,11) and similar places. Is that the interval from 0 to 10? Then why is 20 the interval from 0 to 20? Did she rest between 10 and 20 seconds? Oh dear.
My head hurts.