SOLUTION: I need help in this question. I know that n=15 and p=0.2 and q=0.8. But don't quite understand what the question meant by omits one of the wrong answers and guesses the other 3. Pl

Question 269482: I need help in this question. I know that n=15 and p=0.2 and q=0.8. But don't quite understand what the question meant by omits one of the wrong answers and guesses the other 3. Please help.
A Multiple-choice test has 15 questions with each having 5 possible answers with one correct. Assume a student answers every question, omits one of the wrong answers on each question and randomly guesses among the remaining three choices.
Answer by drk(1908) (Show Source): You can put this solution on YOUR website!
You start with 5 possible answer choices. So if you randomly guess,
P(correct) = .20, and P(incorrect) = .80
To omit one question means remove one answer choice that is obviously wrong. You are left with 4 answer choices, not 3 as stated in the question. So, if you randomly now guess
P(correct) = .25, and P(incorrect) = .75
Now the expression for P( n correct) is

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