A.23 Bivariate normal distribution

The ordered pair (X, Y)T of observations has a bivariate normal distribution, denoted

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if it has joint density

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where

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The means and variances are

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and X and Y have correlation coefficient and covariance

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Most properties follow from those of the ordinary, univariate and normal distribution. One point worth noting (which is clear from the form of the joint density function) is that if X and Y have a bivariate normal distribution, then they are independent if they are uncorrelated (a result which is not true in general).

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