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Math Help - Binomial Probability questions

  1. #1
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    Binomial Probability questions

    1. A dental inspector finds that about 20% of children of a certain area have tooth decay. What is the probability that out of 6children examined, only the first,third and fifth will have tooth decay?

    -> i got (0.2)^2(0.8)^3 =64/3125 but the answer is 64/3125. What am i missing??


    2. On the average a typist has to correct one word in 800words. Assuming that a page contains 200words, find the probability of more than one correction per page.

    -> i got
    1- [200C1(799/800)^199(1/800) + 200C0(799/800)^200] = 0.0264
    But answer is 0.0625
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  2. #2
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    Re: Binomial Probability questions

    1.It's Exactly What You need
    Did You multiplied 200 in first statment?
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  3. #3
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    Re: Binomial Probability questions

    Quote Originally Posted by gahyunkk View Post
    2. On the average a typist has to correct one word in 800words. Assuming that a page contains 200words, find the probability of more than one correction per page.

    -> i got
    1- [200C1(799/800)^199(1/800) + 200C0(799/800)^200] = 0.0264
    But answer is 0.0625
    I think you've done (2) correctly.
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  4. #4
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    Re: Binomial Probability questions

    [QUOTE=gahyunkk;828536]1. A dental inspector finds that about 20% of children of a certain area have tooth decay. What is the probability that out of 6children examined, only the first,third and fifth will have tooth decay?

    -> i got (0.2)^2(0.8)^3 =64/3125 but the answer is 64/3125. What am i missing??
    There are three children with tooth decay so this should be (0.2)^3(0.8)^3= (1/5)^3(4/5)^3= 2^9/5^6. Your "64/3125 but the answer is 64/3125" is very confusing.


    2. On the average a typist has to correct one word in 800words. Assuming that a page contains 200words, find the probability of more than one correction per page.

    -> i got
    1- [200C1(799/800)^199(1/800) + 200C0(799/800)^200] = 0.0264
    But answer is 0.0625
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  5. #5
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    Binomial Probability questions

    Quote Originally Posted by Cartesius24 View Post
    1.It's Exactly What You need
    Did You multiplied 200 in first statment?
    Oh sorry first one if i do 0.2^3x0.8^3 i get
    64/15625 and answer is 64/3125

    And what do u mean by multiplying 200??
    Last edited by gahyunkk; August 16th 2014 at 03:37 PM.
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  6. #6
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    Binomial Probability questions

    [QUOTE=HallsofIvy;828587]

    Sorry i typed wrong thing
    I originally did 0.2^3x0.8^3 but then i get 64/15625 but the answer is 64/3125
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  7. #7
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    Re: Binomial Probability questions

    2^6=15625
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  8. #8
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    Re: Binomial Probability questions

    [QUOTE =Cartesius24;828694]2^6=15625[/QUOTE]
    Why is it 2^6???
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  9. #9
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    Re: Binomial Probability questions

    sorry 5^6
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