Recent content by rhuelu

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    Correlation with two independent variables

    how would you prove this?
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    Correlation with two independent variables

    I would appreciate some help with this problem. Assuming X and Y are independent, I'm trying to find the correlation between XY and Y in terms of the means and standard deviations of X and Y. I'm not sure how to simplify cov(XY,Y)=E(XYY)-E(XY)E(Y) =E(XY^2)-E(X)E(Y)^2. If X and Y are...
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    Graduate Is the Correlation between XY and Y Zero if X and Y are Independent?

    I would appreciate some help with this problem. Assuming X and Y are independent, I'm trying to find the correlation between XY and Y in terms of the means and standard deviations of X and Y. I'm not sure how to simplify cov(XY,Y)=E(XYY)-E(XY)E(Y) =E(XY^2)-E(X)E(Y)^2. If X and Y are...
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    Undergrad Integrating 2 du's: A Scientific Approach

    How would I integrate udu/du ?
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    Proof: Matrix Rank of X = n with Y,Z of Rank n-1,1 Respectively

    it doesn't seem like this is the most formal logic in the world...is it trivial that the matrices constructed have ranks of n-1 and 1 or does this need to be shown as well
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    Proof: Matrix Rank of X = n with Y,Z of Rank n-1,1 Respectively

    I'm trying to show that any matrix X with rank n can be written as the sum of matrices Z and Y with rank n-1 and 1, respectively. Since X,Y, Z have the same dimensions, is this a simple matter of saying pick one of the columns in X with a pivot. Let Z= X with this column replaced by zeroes...
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    Graduate Proving Matrix X rank Decomposition

    How can you prove that matrix X with rank n can be written as the sum of matrices Y and Z where Y has rank n-1 and Z has rank of 1. Thanks!
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    Undergrad Integrating x*(1/2b)*exp(-abs(x-a)/b) - Solution

    nevermind, i got it
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    Undergrad Integrating x*(1/2b)*exp(-abs(x-a)/b) - Solution

    how would I got about finding the value of the integral from negative infinity to positive infinity if I have 2 different expressions depending on the value of x-a?
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    Undergrad Integrating x*(1/2b)*exp(-abs(x-a)/b) - Solution

    oh ok thanks
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    Undergrad Integrating x*(1/2b)*exp(-abs(x-a)/b) - Solution

    I'm not really sure how to deal with the absolute value
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    Undergrad Integrating x*(1/2b)*exp(-abs(x-a)/b) - Solution

    Exactly. Thanks.
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    Undergrad Integrating x*(1/2b)*exp(-abs(x-a)/b) - Solution

    integral of x*(1/2b)*exp(-abs(x-a)/b) sorry about the format, I don't know how to use the signs. this looks like an integration by parts, but I'm not really seeing how to work it out thanks!
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    Undergrad Finding Solutions for a Matrix with Variables: Row Reduction Required?

    here's a tough one... find the values of x for which the matric has no, one, and inf many solutions A= (1 -2 3 1; 2 x 6 6; -1 -3 x-3 0)
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    Graduate Do derivatives belong to unique functions?

    thanks...that makes sense. Do you think this logic still holds if we only know that F(x) is right continuous? This is one of the properties of a cdf.