<PRE><B>Question 671469</B>
A quiz has 7 questions. Each with three possible answers. With random guessing, what is the chance you get EXACTLY 4 questions right. I feel like getting all 7 right would be 1/2187. And getting none right would be 128/2187. But what is the chance of getting EXACTLY 4. Or EXACTLY 3?
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Binomial Problem with n = 7 ; p(correct) = 1/3  ; p(wrong) = 2/3
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P(x = 4) = 7C4*(1/3)^4*(2/3)^3 = 0.1280
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P(x = 3) = 7C3*(1/3)^3*(2/3)^4 = 0.2561
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Cheers,
Stan H.
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