Upper bound for probability of truncated normal random variable












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$begingroup$


Suppose that $X$ and $Z$ are iid with distribution ${mathcal N}(mu,sigma^2)$. $X$ conditional on $d<X<+infty$ has a truncated normal distribution with support $(d,+infty)$. Letting $Y$ denote that random variable, its CDF is



$F(x,mu,sigma,d) = dfrac{PhiBigl(dfrac{x-mu}{sigma}Bigr)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}$.



I've computed $ {rm P} (Y > c+ {rm E}[Z,|, Z< d])$ and I'm trying to find an upper bound that does not depend on $d$. Any help?



begin{align*}
{rm P} (Y > c+ {rm E}[Z,|, Z< d]) = dfrac{Phileft(dfrac{c}{sigma}-dfrac{phiBigl(dfrac{d-mu}{sigma}Bigr)}{PhiBigl(dfrac{d-mu}{sigma}Bigr)}right)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}
end{align*}

where $Phi(cdot)$ and $phi(cdot)$ denote the standard normal CDF and PDF respectively.










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  • 2




    $begingroup$
    $X mid X > d$ is not a random variable. I think you mean $Y = X$ if $X > d$. But what is it if $X le d$?
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 15:50












  • $begingroup$
    $Y$ has a truncated normal distribution with support $(d,+infty)$. I've edited the question to convey that idea.
    $endgroup$
    – capadocia
    Dec 11 '18 at 17:05
















1












$begingroup$


Suppose that $X$ and $Z$ are iid with distribution ${mathcal N}(mu,sigma^2)$. $X$ conditional on $d<X<+infty$ has a truncated normal distribution with support $(d,+infty)$. Letting $Y$ denote that random variable, its CDF is



$F(x,mu,sigma,d) = dfrac{PhiBigl(dfrac{x-mu}{sigma}Bigr)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}$.



I've computed $ {rm P} (Y > c+ {rm E}[Z,|, Z< d])$ and I'm trying to find an upper bound that does not depend on $d$. Any help?



begin{align*}
{rm P} (Y > c+ {rm E}[Z,|, Z< d]) = dfrac{Phileft(dfrac{c}{sigma}-dfrac{phiBigl(dfrac{d-mu}{sigma}Bigr)}{PhiBigl(dfrac{d-mu}{sigma}Bigr)}right)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}
end{align*}

where $Phi(cdot)$ and $phi(cdot)$ denote the standard normal CDF and PDF respectively.










share|cite|improve this question











$endgroup$








  • 2




    $begingroup$
    $X mid X > d$ is not a random variable. I think you mean $Y = X$ if $X > d$. But what is it if $X le d$?
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 15:50












  • $begingroup$
    $Y$ has a truncated normal distribution with support $(d,+infty)$. I've edited the question to convey that idea.
    $endgroup$
    – capadocia
    Dec 11 '18 at 17:05














1












1








1





$begingroup$


Suppose that $X$ and $Z$ are iid with distribution ${mathcal N}(mu,sigma^2)$. $X$ conditional on $d<X<+infty$ has a truncated normal distribution with support $(d,+infty)$. Letting $Y$ denote that random variable, its CDF is



$F(x,mu,sigma,d) = dfrac{PhiBigl(dfrac{x-mu}{sigma}Bigr)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}$.



I've computed $ {rm P} (Y > c+ {rm E}[Z,|, Z< d])$ and I'm trying to find an upper bound that does not depend on $d$. Any help?



begin{align*}
{rm P} (Y > c+ {rm E}[Z,|, Z< d]) = dfrac{Phileft(dfrac{c}{sigma}-dfrac{phiBigl(dfrac{d-mu}{sigma}Bigr)}{PhiBigl(dfrac{d-mu}{sigma}Bigr)}right)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}
end{align*}

where $Phi(cdot)$ and $phi(cdot)$ denote the standard normal CDF and PDF respectively.










share|cite|improve this question











$endgroup$




Suppose that $X$ and $Z$ are iid with distribution ${mathcal N}(mu,sigma^2)$. $X$ conditional on $d<X<+infty$ has a truncated normal distribution with support $(d,+infty)$. Letting $Y$ denote that random variable, its CDF is



$F(x,mu,sigma,d) = dfrac{PhiBigl(dfrac{x-mu}{sigma}Bigr)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}$.



I've computed $ {rm P} (Y > c+ {rm E}[Z,|, Z< d])$ and I'm trying to find an upper bound that does not depend on $d$. Any help?



begin{align*}
{rm P} (Y > c+ {rm E}[Z,|, Z< d]) = dfrac{Phileft(dfrac{c}{sigma}-dfrac{phiBigl(dfrac{d-mu}{sigma}Bigr)}{PhiBigl(dfrac{d-mu}{sigma}Bigr)}right)-PhiBigl(dfrac{d-mu}{sigma}Bigr)}{1-PhiBigl(dfrac{d-mu}{sigma}Bigr)}
end{align*}

where $Phi(cdot)$ and $phi(cdot)$ denote the standard normal CDF and PDF respectively.







probability normal-distribution conditional-probability upper-lower-bounds






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edited Dec 11 '18 at 17:01







capadocia

















asked Dec 11 '18 at 15:38









capadociacapadocia

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  • 2




    $begingroup$
    $X mid X > d$ is not a random variable. I think you mean $Y = X$ if $X > d$. But what is it if $X le d$?
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 15:50












  • $begingroup$
    $Y$ has a truncated normal distribution with support $(d,+infty)$. I've edited the question to convey that idea.
    $endgroup$
    – capadocia
    Dec 11 '18 at 17:05














  • 2




    $begingroup$
    $X mid X > d$ is not a random variable. I think you mean $Y = X$ if $X > d$. But what is it if $X le d$?
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 15:50












  • $begingroup$
    $Y$ has a truncated normal distribution with support $(d,+infty)$. I've edited the question to convey that idea.
    $endgroup$
    – capadocia
    Dec 11 '18 at 17:05








2




2




$begingroup$
$X mid X > d$ is not a random variable. I think you mean $Y = X$ if $X > d$. But what is it if $X le d$?
$endgroup$
– Robert Israel
Dec 11 '18 at 15:50






$begingroup$
$X mid X > d$ is not a random variable. I think you mean $Y = X$ if $X > d$. But what is it if $X le d$?
$endgroup$
– Robert Israel
Dec 11 '18 at 15:50














$begingroup$
$Y$ has a truncated normal distribution with support $(d,+infty)$. I've edited the question to convey that idea.
$endgroup$
– capadocia
Dec 11 '18 at 17:05




$begingroup$
$Y$ has a truncated normal distribution with support $(d,+infty)$. I've edited the question to convey that idea.
$endgroup$
– capadocia
Dec 11 '18 at 17:05










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$E [Z|Z<d] < mu$, so $P(Y > c + E[Z|Z<d]) ge P(Y > c+mu)$. But if $d > c+mu$, $P(Y > c+mu) = 1$. So the best upper bound you can have that doesn't depend on $d$ is $1$.






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    $begingroup$

    $E [Z|Z<d] < mu$, so $P(Y > c + E[Z|Z<d]) ge P(Y > c+mu)$. But if $d > c+mu$, $P(Y > c+mu) = 1$. So the best upper bound you can have that doesn't depend on $d$ is $1$.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      $E [Z|Z<d] < mu$, so $P(Y > c + E[Z|Z<d]) ge P(Y > c+mu)$. But if $d > c+mu$, $P(Y > c+mu) = 1$. So the best upper bound you can have that doesn't depend on $d$ is $1$.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        $E [Z|Z<d] < mu$, so $P(Y > c + E[Z|Z<d]) ge P(Y > c+mu)$. But if $d > c+mu$, $P(Y > c+mu) = 1$. So the best upper bound you can have that doesn't depend on $d$ is $1$.






        share|cite|improve this answer









        $endgroup$



        $E [Z|Z<d] < mu$, so $P(Y > c + E[Z|Z<d]) ge P(Y > c+mu)$. But if $d > c+mu$, $P(Y > c+mu) = 1$. So the best upper bound you can have that doesn't depend on $d$ is $1$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 11 '18 at 17:20









        Robert IsraelRobert Israel

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        322k23212465






























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