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    Question uno.
    Given that lamda = 2.2 and P(X=x) = 0.1967 fiind the value of x.

    So I subed it in the equation to work out Px and I got:
    (2.2^x)/x! = 0.1967/e^-2.2

    But I can't seem to solve this would I just have to do it trial and error?




    Question dos.
    Suppose that for a positive integer x,
    P(X=x-1)<=P(X=x) and P(X=x+1)<P(X=x)
    Determine in terms of x, the possible range of values for lambda.
    =/ Like I'm using the formula thing: Px=lamda/P(x-1)

    But it's not really working. It seems like the question is wrong....
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    (Original post by SmileyGurl13)
    Question uno.
    Given that lamda = 2.2 and P(X=x) = 0.1967 fiind the value of x.

    So I subed it in the equation to work out Px and I got:
    (2.2^x)/x! = 0.1967/e^-2.2

    But I can't seem to solve this would I just have to do it trial and error?
    You are not going to get an analytic solution. You just need to try values for x and see which one fits the bill.



    Question dos.
    Suppose that for a positive integer x,
    P(X=x-1)<=P(X=x) and P(X=x+1)<P(X=x)
    Determine in terms of x, the possible range of values for lambda.
    =/ Like I'm using the formula thing: Px=lamda/P(x-1)

    But it's not really working. It seems like the question is wrong....
    So what have you done?

    PS: Don't recognize that formula; you might want to check it.
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    (Original post by ghostwalker)
    You are not going to get an analytic solution. You just need to try values for x and see which one fits the bill.




    So what have you done?

    PS: Don't recognize that formula; you might want to check it.
    Okie for 1

    And the formula is:

    P(X=x)=lambda/x * P(X=x-1)
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    The formula for a Poisson distribution is:



    It has an r! in it - r is what you want to find, and because of the r! you know r is a positive integer. So just start at one and go up. It didn't take me too long is your only hint.
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    (Original post by SmileyGurl13)
    And the formula is:

    P(X=x)=lambda/x * P(X=x-1)
    That looks more like it. So, what have you done with it?
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    (Original post by ghostwalker)
    That looks more like it. So, what have you done with it?

    Well I said P(X=x-1) = x/lamda P(X=x)

    so x/lambda P(X=x) <= P(x=x)
    therefore x/lamda<=1
    so lamda>=x

    And P(x=x+1) = lamda/xP(x=x)

    So lamda/xP(x=x)<P(X=x)
    so lamda/x<1

    so lamda<x

    which is contradictoray :/
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    (Original post by tcb1992)
    The formula for a Poisson distribution is:



    It has an r! in it - r is what you want to find, and because of the r! you know r is a positive integer. So just start at one and go up. It didn't take me too long is your only hint.
    Yeah I've got it now thanks
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    (Original post by SmileyGurl13)
    And P(x=x+1) = lamda/xP(x=x)

    So lamda/xP(x=x)<P(X=x)
    so lamda/x<1

    so lamda<x

    which is contradictoray :/
    That's not correct, but from your latter post, I presume you've sorted it now.

    But just for the record.

    P(x=x+1) = lamda/(x+1) * P(x=x)

    And you have \lambda\le x+1
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    (Original post by ghostwalker)
    That's not correct, but from your latter post, I presume you've sorted it now.

    But just for the record.

    P(x=x+1) = lamda/(x+1) * P(x=x)

    And you have \lambda\le x+1
    No I haven't got it :P I meant I'd got the first question, Can you explain how you got P(x=x+1) = lamda/(x+1) * P(x=x) thanks
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    Poisson is French for fish. If that's the help you're after.
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    (Original post by SmileyGurl13)
    No I haven't got it :P I meant I'd got the first question, Can you explain how you got P(x=x+1) = lamda/(x+1) * P(x=x) thanks
    That's just the original equation you had evaluated at "x+1" rather than at "x".

    Alternatively, you would write down P(x+1) from the definition of the poisson distribution, and similarly P(x), then work out what P(x+1)/P(x) equals, and you will get that equation.
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    (Original post by ghostwalker)
    That's just the original equation you had evaluated at "x+1" rather than at "x".

    Alternatively, you would write down P(x+1) from the definition of the poisson distribution, and similarly P(x), then work out what P(x+1)/P(x) equals, and you will get that equation.
    thank you very much you've helped a lot. +ve rep coming your way

    I may be asking for help in the future, cos I can't ask teachers as I'm self-studying :| is tht okay?
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    (Original post by SmileyGurl13)
    thank you very much you've helped a lot. +ve rep coming your way
    Cheers.

    I may be asking for help in the future, cos I can't ask teachers as I'm self-studying :| is tht okay?
    That's what the forum is here for.
 
 
 
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