My wife's second cousin was taking a tech course to be an electrician. He showed me some homework he was having trouble completing. Would you believe it. The subject was transistor audio amplifiers. On the paper there was a schematic of an amplifier and a list of questions about the circuit. I was amazed by what I saw- there were two major errors on the amp schematic which meant that no one could have sorted out what was going on. This was a standard course paper that had been in use for years.
That's remarkably common
I've found numerous such examples in exams over the years - generally exams are set and marked by people you don't understand the subject.
I was a finalist a number of years (I won it twice) in the Sharp Electronics UK Engineer of the Year competition - the finals were held in nice hotels, and various events or trips were included. Anyway, in one final we all came out of the exam moaning like mad about one of the questions - this particular one was multiple choice, and none of the answers was correct. We approached the Sharp guys, who we all knew, and complained bitterly about question 8 (or whatever number it was) - to be told it was Jim who set the paper - so we all hunted down Jim
His 'excuse' was that he had compiled the questions from a number of sources, and hadn't actually checked them his self - but at least he was technical, and didn't bother checking - many exams are compiled in a similar war, but by people who don't understand the questions at all. I'd like to think that if I was compiling an exam paper I'd make damn sure there weren't any silly mistakes in it.
Incidentally, I (along with many of the other contestants) added an extra answer box with the correct answer, and ticked that one - but as we all complained long before the papers were marked (to the actual people who would be marking them) I presume that question was ignored.