Derivative of CDF of Multivariate (Normal) Distribution












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I am trying to get derivative of some probability functions and I do not know if it would is correct to use the following method. As an example, I am interested in derivative of $f(Q)$ with respect to $Q$.



$$f(Q)=Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$$



where $epsilon_i$, $epsilon_1$, $epsilon_2$, are independent normal distribution with mean $0$ and variance $sigma^2$, and $gamma$ is independent of all $epsilon$s and is normal with mean $mu$ and standard deviation of $s^2$.



1- With abuse of notations (I know it does not make sense to have $epsilon_i$ equal to anything), can I say



$$f'(Q)=Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
-Pr(epsilon_i+gamma<Q, epsilon_2+gamma=Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
+Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma=Q),$$



where
$Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$, for example, is the derivative of joint distribution of $(epsilon_i+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q) minus the
derivative of the CDF of joint distribution of $(epsilon_i+gamma,epsilon_2+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q,Q).



2- Can I simplify the first term for example as follow?
$$Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)=
Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$$
.



Then what is $Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$ exactly?



3- How can I simplify $f'(Q)$ to be able to numerically compute it easily?










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    0












    $begingroup$


    I am trying to get derivative of some probability functions and I do not know if it would is correct to use the following method. As an example, I am interested in derivative of $f(Q)$ with respect to $Q$.



    $$f(Q)=Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$$



    where $epsilon_i$, $epsilon_1$, $epsilon_2$, are independent normal distribution with mean $0$ and variance $sigma^2$, and $gamma$ is independent of all $epsilon$s and is normal with mean $mu$ and standard deviation of $s^2$.



    1- With abuse of notations (I know it does not make sense to have $epsilon_i$ equal to anything), can I say



    $$f'(Q)=Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
    -Pr(epsilon_i+gamma<Q, epsilon_2+gamma=Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
    +Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma=Q),$$



    where
    $Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$, for example, is the derivative of joint distribution of $(epsilon_i+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q) minus the
    derivative of the CDF of joint distribution of $(epsilon_i+gamma,epsilon_2+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q,Q).



    2- Can I simplify the first term for example as follow?
    $$Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)=
    Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$$
    .



    Then what is $Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$ exactly?



    3- How can I simplify $f'(Q)$ to be able to numerically compute it easily?










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      I am trying to get derivative of some probability functions and I do not know if it would is correct to use the following method. As an example, I am interested in derivative of $f(Q)$ with respect to $Q$.



      $$f(Q)=Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$$



      where $epsilon_i$, $epsilon_1$, $epsilon_2$, are independent normal distribution with mean $0$ and variance $sigma^2$, and $gamma$ is independent of all $epsilon$s and is normal with mean $mu$ and standard deviation of $s^2$.



      1- With abuse of notations (I know it does not make sense to have $epsilon_i$ equal to anything), can I say



      $$f'(Q)=Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
      -Pr(epsilon_i+gamma<Q, epsilon_2+gamma=Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
      +Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma=Q),$$



      where
      $Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$, for example, is the derivative of joint distribution of $(epsilon_i+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q) minus the
      derivative of the CDF of joint distribution of $(epsilon_i+gamma,epsilon_2+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q,Q).



      2- Can I simplify the first term for example as follow?
      $$Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)=
      Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$$
      .



      Then what is $Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$ exactly?



      3- How can I simplify $f'(Q)$ to be able to numerically compute it easily?










      share|cite|improve this question











      $endgroup$




      I am trying to get derivative of some probability functions and I do not know if it would is correct to use the following method. As an example, I am interested in derivative of $f(Q)$ with respect to $Q$.



      $$f(Q)=Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$$



      where $epsilon_i$, $epsilon_1$, $epsilon_2$, are independent normal distribution with mean $0$ and variance $sigma^2$, and $gamma$ is independent of all $epsilon$s and is normal with mean $mu$ and standard deviation of $s^2$.



      1- With abuse of notations (I know it does not make sense to have $epsilon_i$ equal to anything), can I say



      $$f'(Q)=Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
      -Pr(epsilon_i+gamma<Q, epsilon_2+gamma=Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)
      +Pr(epsilon_i+gamma<Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma=Q),$$



      where
      $Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)$, for example, is the derivative of joint distribution of $(epsilon_i+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q) minus the
      derivative of the CDF of joint distribution of $(epsilon_i+gamma,epsilon_2+gamma,frac{epsilon_i+epsilon_1}{2}+gamma)$ with respect to the first term at (Q,Q,Q).



      2- Can I simplify the first term for example as follow?
      $$Pr(epsilon_i+gamma=Q, epsilon_2+gamma>Q, frac{epsilon_i+epsilon_1}{2}+gamma<Q)=
      Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$$
      .



      Then what is $Pr(epsilon_i+gamma=Q, epsilon_2>epsilon_i>epsilon_1)$ exactly?



      3- How can I simplify $f'(Q)$ to be able to numerically compute it easily?







      calculus probability derivatives normal-distribution






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      edited Jan 9 at 14:17







      Neda Kh

















      asked Jan 9 at 13:43









      Neda KhNeda Kh

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