Recent content by sandsifter

  1. S

    Determining the covariance matrix of a multivariate normal distribution

    Jason, You are right. I took it for granted that the normal approximation is valid (it probably is close enough, but your last statement is making me think a little bit...). My aim was to use the Mahalanobis distance to see if certain data sets were close to a certain model (e.g. in my...
  2. S

    Determining the covariance matrix of a multivariate normal distribution

    I will try to rephrase the question in a more general way. I have 3 dependent variables, X, Y and Z. I know their marginal distributions (which are normal) and I know roughly how they move together: X+Y+Z = constant and if I increase X, Y will on average decrease by a proportional amount...
  3. S

    Determining the covariance matrix of a multivariate normal distribution

    Hi all, I have a stats problem I'm trying to figure out. Suppose I have a very large population (~millions) of colored balls with exactly 50% red, 30% green, 20% blue. If I take a random sample of 1000 of these balls, the distribution of colors I end up with can be modeled as a multivariate...
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