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  1. #1
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    poisson distribution

    i am having problem with part iv ) . the ans is 0.04519 . can anyone tell me how to do this ? i have solved part i , ii and iii





    poisson distribution-img_20140820_172031-1-.jpg
    poisson distribution-img_20140820_171710-1-.jpg
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  2. #2
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    Re: poisson distribution

    figure out $\lambda$ for the distribution from the wording of the problem and then evaluate the Poisson CDF for 3.
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    Re: poisson distribution

    Quote Originally Posted by romsek View Post
    figure out $\lambda$ for the distribution from the wording of the problem and then evaluate the Poisson CDF for 3.
    Ignore the last post... I could have sworn you originally asked about (ii).

    We can't see (iv) in your image.
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    Re: poisson distribution

    Quote Originally Posted by romsek View Post
    Ignore the last post... I could have sworn you originally asked about (ii).

    We can't see (iv) in your image.
    sorry. it's my fault . part iv)

    6 test tube contains a total number of 5 bacteria.
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    Re: poisson distribution

    Quote Originally Posted by delso View Post
    sorry. it's my fault . part iv)

    6 test tube contains a total number of 5 bacteria.
    looking deeper at this ... It's not a Poisson distribution we're talking about here. It's a binomial distribution.

    Your image cuts off the initial amount of water. Your work seems to indicate it's $10^5cc$ is that correct?
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    Re: poisson distribution

    Quote Originally Posted by romsek View Post
    looking deeper at this ... It's not a Poisson distribution we're talking about here. It's a binomial distribution.

    Your image cuts off the initial amount of water. Your work seems to indicate it's $10^5cc$ is that correct?
    yes , it's $10^5cc$ of water.. i still cant get the ans. can anyone explain further?
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    Re: poisson distribution

    Quote Originally Posted by romsek View Post
    looking deeper at this ... It's not a Poisson distribution we're talking about here. It's a binomial distribution.

    Your image cuts off the initial amount of water. Your work seems to indicate it's $10^5cc$ is that correct?
    A water tank contains 10^5 cm3 of water that is free from bacteria. A number of 1800 bacteria were added to water and water is stirred to disrtibute the bactria randomly. Then 6 test tube were filled with 20cm3 of this water. Findthe probablity of
    a) a test tube contain 3 bactria
    b) A test tube contain at least 3 bacteria
    c) exactly 4 out of 6 test tube with each contain 3 bacteria

    d) 6 test tube conatin a total of 5 bacteria

    i got stucked at part d .
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    Re: poisson distribution

    How did You calculate that what You have?
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    Re: poisson distribution

    Quote Originally Posted by delso View Post
    A water tank contains 10^5 cm3 of water that is free from bacteria. A number of 1800 bacteria were added to water and water is stirred to disrtibute the bactria randomly.
    So there are an average of 1800/10000= 18/100= 9/50 "bacteria per cm".
    Then 6 test tube were filled with 20cm3 of this water. Findthe probablity of
    (9/50)(20)= 18/5 bacteria per test tube.

    a) a test tube contain 3 bactria
    b) A test tube contain at least 3 bacteria
    These two problems can be done using the Poisson distribution with \lambda= 18/5. (a) is P(3) and (b) is 1- (P(0)+ P(1)+ P(2)).

    c) exactly 4 out of 6 test tube with each contain 3 bacteria
    This requires, as romsek said, the binomial distribution with p= the probability you got in (a)

    d) 6 test tube conatin a total of 5 bacteria [/quote]
    How many different ways can 5 bacteria be in 6 specified test tubes? They could all 5 be in one test tube, or 5 in one test tube and one in another, or 3 in one test tube and 2 in another, or 3 in one test tube and 1 in each of two other test tubes, etc.

    i got stucked at part d .[/QUOTE]
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    Re: poisson distribution

    i got stucked at part d .[/QUOTE][/QUOTE]
    d) 6 test tube conatin a total of 5 bacteria [/quote]
    How many different ways can 5 bacteria be in 6 specified test tubes? They could all 5 be in one test tube, or 5 in one test tube and one in another, or 3 in one test tube and 2 in another, or 3 in one test tube and 1 in each of two other test tubes, etc.

    for part d , can you show me all the possibility of having 5 bacteria in 6 test tube? any other easy method to get the ans for this? it seems quite complicated if i do in this way..
    Last edited by delso; August 23rd 2014 at 07:40 PM.
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    Re: poisson distribution

    double post~
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