In given Example, we determined the probability that you could guess your way to a passing score on a quiz with 15 true-false questions. If you did guess at each of 15 true-false questions, what is the expected value of X = number of correct answers? Is the expected value a possible score on the quiz? What exactly does the expected value tell us?
Example
Guessing Your Way to a Passing Score You have been busy lately, so busy that you're surprised to learn when you arrive at today's statistics class that a 15-question true-false quiz is on the agenda. The quiz is about readings that you haven't done, so you are forced to guess at every question. You will pass the quiz if you get ten or more correct answers, so you wonder about P(X ≥ 10), where X = number of correct answers.