Question

In a multiple choice test, each question has five options. Sutdents will get 5 points for each correct answer; lose 2 points for each incorrect answer; and receive no points for unanswered questions. A student does not know the correct answer for one question. Is it to her advantage or disadvantage to guess an answer? Show calculations for expected value.

Answer 1

disadvantage, 5 questions means a 1/5 chance of it being correct. every 5 questions you would recive 5 points - 8. 5-8=-3..... so negative 3.