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  • Users: laz0r
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  1. L

    Conditional Probability Question

    Homework Statement Suppose there are two urns that contain white and yellow balls. Urn 1 contains 10 white and 5 yellow balls, and Urn 2 contains 6 white and 12 yellow balls. You are going to draw 3 balls without replacement from one of the urns. To decide which urn to draw from, you will...
  2. L

    Probability/Combinatorics Question

    Thanks for the reassurance, I appreciate it. I don't have much experience in the math stats setting as I recently switched into the Statistics major, but I think I'm getting the hang of it.
  3. L

    Probability/Combinatorics Question

    Homework Statement The NHL currently has a total of 30 teams in 4 divisions (7 teams in the Pacific Division, 7 in the Central Division, 8 in the Metropolitan Division, and 8 in the Atlantic Division). Suppose the NHL gets a new commissioner, and they have the curious notion of...
  4. L

    Statistics Sum of Squares x*y Proof

    Sorry, I'm very slow at typing this latex code.. \overline{y}*[\sum(\overline{x} - x_{i})] = 0 [\sum(\overline{x} - x_{i})] = 0 \sum(\overline{x}) - \sum(x_{i}) = 0 n(\overline{x}) - n(\overline{x}) = 0 LHS = RHS used \sum(c) = n*c Where n is the upper bound and 1 is the lower...
  5. L

    Statistics Sum of Squares x*y Proof

    Wow, it appears my brain took a nap today. Thank you for your help lol, I appreciate it.
  6. L

    Statistics Sum of Squares x*y Proof

    They're related by \overline{x} = [\sum x_{i}]/n
  7. L

    Statistics Sum of Squares x*y Proof

    I'm a little bit rusty on my operation of sums, so excuse me if this is incorrect, but can I do this? [(\overline{y})/n][\sum x_{i}] - \overline{y}[\sum x_{i}] = [(\overline{y}^2)/n][\sum(x_{i} - x_{i})] Then what tends to zero appears to be obvious
  8. L

    Statistics Sum of Squares x*y Proof

    I've figured out why, but I'm not sure how to explain it symbolically, do you think I would need to elaborate more or is my edited explanation good enough in your view? Thanks for the help!
  9. L

    Statistics Sum of Squares x*y Proof

    Ok, so I actually did end up getting somewhere and didn't realize it =) EDIT: I've done proof \sum[(x_{i}-\overline{x})y_{i}] + \sum[\overline{y}(\overline{x} - x_{i})] Playing around in excel has taught me that \sum[\overline{y}(\overline{x} - x_{i})] is actually just equal to...
  10. L

    Statistics Sum of Squares x*y Proof

    Homework Statement Prove that \sum[(x_{i} - \overline{x})(y_{i} - \overline{y})] = \sum[(x_{i} - \overline{x})y_{i}] Homework Equations None. The Attempt at a Solution I tried using the fact that the sum of the mean values is just the mean value, because the sum of a constant...
  11. L

    Is Vector Calculus Needed for Statistics?

    Thanks for all the replies, I'm actually not planning on pursuing anything past a Master's degree in statistics, I'd like to get into the industry as soon as possible. I'll definitely look into expanding my knowledge of linear algebra, as I know it's used quite a lot in statistics. I'll also...
  12. L

    Is Vector Calculus Needed for Statistics?

    Yeah, I'm just finishing a mathematical statistics course right now (the first of two) and it is somewhat centered around proofs. That being said, I found it to be an alright class to take. I'll probably go ahead and take more linear algebra instead of vector calculus, as I have room for it.
  13. L

    Is Vector Calculus Needed for Statistics?

    Well this course isn't even required for my degree, I'm just wondering if it's worth taking it. My current major is statistics.
  14. L

    Is Vector Calculus Needed for Statistics?

    I've taken a multi-variable calculus course already that covers infinite sequences and series, Taylor's theorem, quadratics surfaces, double and triple integration etc. I'm looking to get a Master's Degree in statistics two years from now, is there any point of me taking a class that involves...
  15. L

    Equation of an Upward Facing Cone

    I'm having a little bit of trouble understanding the equation of a cone.. It is given by (x^2)/(a^2) + (y^2)/(b^2) = (z^2)/(c^2) I understand that if a ≠ b you have an elliptical cone, but I'm not sure how to set the equation up to define the cone as having a height. Can anyone clarify...
  16. L

    Auxiliary Field H Problem, Asks for Magnetic Field etc

    Ah ok, I understand now. INT[J*dA] = Ifree, then you can use that for your H field later on and find the expression for c immediately by rearranging.
  17. L

    Auxiliary Field H Problem, Asks for Magnetic Field etc

    Homework Statement Homework Equations int[H*dl] = I fenc ∇×H = cr^2 [Khat] ∇×H = Jf The Attempt at a Solution The textbook I have been assigned (griffiths) only deals with currents that are uniformly distributed and I'm not sure how to go about calculating the free...
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