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Statistics: Please calculate my chance of passing the exam

  1. Dec 3, 2008 #1
    I had a MCQ exam today. 90 Questions with 4 alternatives. I need help calculating my chances of passing (which should be really small).

    I know 3 of my answers are correct. I gambled on the rest.

    Also, please calculate the chance of passing, assuming that my guesses were a little more educated, so that the chance of hitting the correct answer was 1/3 instead of 1/4.

    I need 36/90 correct to pass.
     
  2. jcsd
  3. Dec 3, 2008 #2

    CRGreathouse

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    Science Advisor
    Homework Helper

    It's actually not too bad, since the passing grade is low. You need at least 33 out of 87 (since 3 are known to be correct), which is close to the 29 you'd expect guessing 1:3.

    Pari tells me:
    Code (Text):
    sum(k=0,87-33,2.^k*binomial(87,k))/3^87
    0 ms.
    0.2117180908186974588873520067
    you have a 21.2% chance.
     
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