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Thread: i hope i make JohnM and quark proud

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    Talking i hope i make JohnM and quark proud





    okay i managed to do a bonus question on my "take home test" (which is kinda .
    I just want to see if I did it right and answered it right bare with me....
    IF I DID NOT DO OR ANSWER IT RIGHT DO NOT TELL ME HOW!!!

    A student takes a 9 question multiple choice test by guessing. Each question has 5 choices. What is the probability that at least 4 are correct?

    P(X) =
    n! x (n-x)
    _________ *p * q
    (n-x)!x!
    n=9
    x=4
    p=4/9
    q=5/9

    using these values,
    i got 26%
    please tell me I did this correct
    And I do want to know how you are making out of this website, because i told everybody in my statistics class!!!!!
    p.s

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    We're always proud of students who try!

    With this problem, you started on the right track. Make sure the binomial formula includes p^x and q^(n-x).

    p = probability of success
    q = 1-p

    You need to think how "success" is defined in this problem - it's the probability of getting 1 question correct by guessing the correct answer out of 5 choices.

    Then you need to find the probability of getting 0 correct, 1 correct, 2 correct, and 3 correct. Add these up, then subtract this sum from 1.

    In a binomial probability distribution (any distribution, for that matter), the sum of all the probabilities equal 1. So, the probability of getting 4 or more correct is equal to 1 minus the probability of getting 3 or less.

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    Hilary,

    Since there are five choices in each question, p=1/5, and q=4/5.

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    Talking woo hoo (I hope)



    64.42%


    is this it?????????
    hilary

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    Hilary,

    The probability of:

    0 correct = 0.1342
    1 correct = 0.302
    2 correct = 0.302
    3 correct = 0.1762

    Add these up and subtract the sum from 1.

    The answer is 0.0856, or around 8.5% chance of guessing 4 or more questions correctly.

    Think it through - if you had to completely guess on 9 questions, and the probability of getting any particular question correct is only 20%, it's going to be really hard to guess 4 or more correctly.

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    Wink finally figured it out, just read and think it through



    okay
    i did not have to change p=1/5 and q=4/5
    i just had to change the
    n! / (n-X)X! formula
    n=9
    and x=0, x=1, x=2, x=3, for each formula
    and the p^n and q^(n-x)

    i finally figured it out thanks sgain
    p.s I am still stuck on the 175 words per minute,with a standard dev. of 20, the top 3% of the class is to receive a special award, what is the min
    but do not tell me, you have helped me enough. I will get it and let you know what I come up with

    thanks again quark and JohnM

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