Here is a question that might be simple, though I am stuck on it:)
If you get 1/4 of a point deducted from your score if you answer a question incorrectly, is it worth it at the last few minutes of your test to fill in all of the questions with the same letter because the chances are that 1/4 of them will be right (especially if you can deduct some of the obvious wrong answers)? They tell you not to guess, but to me it seems like it is worth a shot since you will probably get at least 1/4 right.
Well, you have a 1/5 chance of getting a question right when you guess randomly. So if you guess on 5 questions, the likelihood is that you’ll get 1 right and 5 wrong. That’s +1, and –4(1/4), for a grand total of 0. Same as if you left them all blank.
Of course, there’s also a chance you’ll get lucky and gain a point or two, and also a chance you’ll get unlucky and come out behind…
I’ve written a fair amount about guessing and how this math works in the past. See here.