Is taking $3sigma$ limits for bivariate correlated random variables as the confidence limits an under estimation?

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If the two random variables are uncorrelated, $3sigma$ limit would mean that the random variables lie inside a hyperrectangle with center coordinates being means of random variables. But if two random variables are correlated, is taking a hyperrectangle instead of corresponding hyperellipsoid an under-approximation or altogether not theoretically correct?







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  • Suppose you are talking about constructing a confidence region for Bivariate normal, then you may refer to, e.g. stats.stackexchange.com/questions/29860/… for using Hotelling's T to construct the region. Note that the region formed by the Cartaesian product of the marginal CI have a lower coverage probability, and it is not optimal in the sense that the volume of the region is larger.
    – BGM
    Jul 25 at 16:45














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If the two random variables are uncorrelated, $3sigma$ limit would mean that the random variables lie inside a hyperrectangle with center coordinates being means of random variables. But if two random variables are correlated, is taking a hyperrectangle instead of corresponding hyperellipsoid an under-approximation or altogether not theoretically correct?







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  • Suppose you are talking about constructing a confidence region for Bivariate normal, then you may refer to, e.g. stats.stackexchange.com/questions/29860/… for using Hotelling's T to construct the region. Note that the region formed by the Cartaesian product of the marginal CI have a lower coverage probability, and it is not optimal in the sense that the volume of the region is larger.
    – BGM
    Jul 25 at 16:45












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If the two random variables are uncorrelated, $3sigma$ limit would mean that the random variables lie inside a hyperrectangle with center coordinates being means of random variables. But if two random variables are correlated, is taking a hyperrectangle instead of corresponding hyperellipsoid an under-approximation or altogether not theoretically correct?







share|cite|improve this question











If the two random variables are uncorrelated, $3sigma$ limit would mean that the random variables lie inside a hyperrectangle with center coordinates being means of random variables. But if two random variables are correlated, is taking a hyperrectangle instead of corresponding hyperellipsoid an under-approximation or altogether not theoretically correct?









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asked Jul 25 at 14:30









NavE3n Naveen

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  • Suppose you are talking about constructing a confidence region for Bivariate normal, then you may refer to, e.g. stats.stackexchange.com/questions/29860/… for using Hotelling's T to construct the region. Note that the region formed by the Cartaesian product of the marginal CI have a lower coverage probability, and it is not optimal in the sense that the volume of the region is larger.
    – BGM
    Jul 25 at 16:45
















  • Suppose you are talking about constructing a confidence region for Bivariate normal, then you may refer to, e.g. stats.stackexchange.com/questions/29860/… for using Hotelling's T to construct the region. Note that the region formed by the Cartaesian product of the marginal CI have a lower coverage probability, and it is not optimal in the sense that the volume of the region is larger.
    – BGM
    Jul 25 at 16:45















Suppose you are talking about constructing a confidence region for Bivariate normal, then you may refer to, e.g. stats.stackexchange.com/questions/29860/… for using Hotelling's T to construct the region. Note that the region formed by the Cartaesian product of the marginal CI have a lower coverage probability, and it is not optimal in the sense that the volume of the region is larger.
– BGM
Jul 25 at 16:45




Suppose you are talking about constructing a confidence region for Bivariate normal, then you may refer to, e.g. stats.stackexchange.com/questions/29860/… for using Hotelling's T to construct the region. Note that the region formed by the Cartaesian product of the marginal CI have a lower coverage probability, and it is not optimal in the sense that the volume of the region is larger.
– BGM
Jul 25 at 16:45















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