SOLUTION: Hello, Can someone help me with this, I am sorry I been out of school for 15 years, and I lost, I don't know where to start. In a multiple-choice test, each question has five op

Question 361832: Hello, Can someone help me with this, I am sorry I been out of school for 15 years, and I lost, I don't know where to start.
In a multiple-choice test, each question has five options. Students will get 2 points for each correct answer; lose 1 point 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 your calculations for expected value
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

The probability of guessing the correct answer at random from 5 choices is

, so the probability of selecting the incorrect answer is

So the expected value of a guess would be

Since the expected value of a guess is smaller than the guaranteed value of not answering, it is disadvantageous to guess in this situation.

Super Double Plus Extra Credit

Let's say that you knew enough so that you were able to eliminate 1, 2, or 3 of the choices, leaving you to guess 1 out of 4, 1 out of 3, or 1 out of 2. Is it ever an even bet or even advantageous to guess?

John

My calculator said it, I believe it, that settles it

The Out Campaign: Scarlet Letter of Atheism

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