The ghost in the exam
Millions of people cheerfully and indiscreetly post details of their personal lives on the Internet, forgetting that Internet posts have a kind of digital immortality. Thanks to archiving and caching systems, erasing a post doesn't necessarily make it go away.
It's also true of education websites, such as the one where I have occasionally posted exam keys for the benefit of my students. One diligent young fellow nosed about through the Intertubes till he dredged up a cache of some of my old posts, although they had been deleted from the original website. Eureka!
He took careful note of his discovery. In fact, the evidence suggests he memorized some of the indicated results. He must have been quite proud of his achievement when he encountered and quickly recognized the following graph on his math exam:
It looked so familiar! When the accompanying problem asked him for the values of f(−5) and f(3), he promptly and confidently wrote down 5 and 7. Amazing! And both wrong!
I tend to rewrite—or at least tweak—my exams. He didn't notice that I had changed the figure from the one he had seen:
Yeah, that was the one where f(−5) = 5 and f(3)= 7. His on-line explorations had led him astray.
He really should have spent the time studying instead.
