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    4 options 30 questions. he wants the probability of someone passing the test by guessing the answer to each question to be 10% or less. what is the lowest score that should be set as the pass mark?

    If anyone could help it would be great
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    (Original post by Morgan111)
    4 options 30 questions. he wants the probability of someone passing the test by guessing the answer to each question to be 10% or less. what is the lowest score that should be set as the pass mark?

    If anyone could help it would be great
    Can you please post your thoughts and all your working?
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    I know X~B(30,0.25) letting X be the probability that a student gets a question right by guessing.

    And that it’s asking for P(X<x) <0.1 but I don’t know where to go from there.
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    (Original post by Morgan111)
    I know X~B(30,0.25) letting X be the probability that a student gets a question right by guessing.

    And that it’s asking for P(X<x) <0.1 but I don’t know where to go from there.
    Are you doing old spec or new spec A Level?

    You could either use a calculator to try different values of x until you get < 0.1. Or you could use probability tables which may be quicker if you've used them before?
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    Ok thank you ☺️ can’t believe I didn’t think of that !
    (And old spec)
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