limsup of a sequence of random variables (definition)convergence of sequence of random variables and cauchy sequencesConvergence of discrete random variables, show $fracS_nsqrtnto0$ a.s.Prove that limsup and liminf of an independent sequence are independent of finite number of termsSequence of Independent random variables$liminf$ and $limsup$ of events and random variablesIs it correct to say that ($colorred( limsup |W_k|/kcolorred) le 1) supseteq limsup colorred(|W_k|/k le 1colorred)$?Further clarification on the connection between limsup and liminf for sequences of sets and real numbers$limsup$ sequence independent $mathcalN(0,sigma^2)$soft question about a sequence of random variables that a.s. convergesInterchangeability of $limsup$

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limsup of a sequence of random variables (definition)


convergence of sequence of random variables and cauchy sequencesConvergence of discrete random variables, show $fracS_nsqrtnto0$ a.s.Prove that limsup and liminf of an independent sequence are independent of finite number of termsSequence of Independent random variables$liminf$ and $limsup$ of events and random variablesIs it correct to say that ($colorred( limsup |W_k|/kcolorred) le 1) supseteq limsup colorred(|W_k|/k le 1colorred)$?Further clarification on the connection between limsup and liminf for sequences of sets and real numbers$limsup$ sequence independent $mathcalN(0,sigma^2)$soft question about a sequence of random variables that a.s. convergesInterchangeability of $limsup$













3












$begingroup$


Let $X_n$ be a sequence of random variables.



First, $limsup X_n=inf_nsup_mge nX_m$. So,



$$limsup X_nle c=bigcup_nbigcap_mge nX_mle c$$



Is it correct to say that if $PX_nle c text i.o.equiv PlimsupX_nle c=1$ then $limsup X_nle c text a.s.$?



Edit 1:



By the same way



$$liminf X_nge c=bigcup_nbigcap_mge nX_mge c$$



So, $PX_nge c text i.o.=1 Rightarrow liminf X_nge c text a.s.$



Edit 2:



Following @Did's comments, the answer follows from



$$[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c] text and [X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$$










share|cite|improve this question











$endgroup$











  • $begingroup$
    your question needs repairs.
    $endgroup$
    – drhab
    Oct 4 '14 at 9:40










  • $begingroup$
    @drhab pls explain...
    $endgroup$
    – d.k.o.
    Oct 4 '14 at 9:55










  • $begingroup$
    $Pleft X_ngeq c: i.oright Rightarrow$... How can a value on its own imply something?
    $endgroup$
    – drhab
    Oct 4 '14 at 9:59






  • 2




    $begingroup$
    The third line is wrong. In general, $$limsup X_nle cnebigcup_nbigcap_mge nX_mle c=liminfX_nle c.$$ (I corrected the typo $X_n$ for $X_m$.) It is not even always true that $$limsup X_nle c=limsupX_nle c.$$ For example, if $X_n(omega)=c+1/n$ for every $n$, then $limsup X_n(omega)=lim X_n(omega)=c$ hence $omega$ is in the event $limsup X_nle c$ but $X_n(omega)gt c$ for every $n$ hence $omega$ is neither in the event $limsupX_nle c$ nor in the event $liminfX_nle c$.
    $endgroup$
    – Did
    Oct 4 '14 at 10:36







  • 2




    $begingroup$
    $[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c]$ and $[X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$ $.
    $endgroup$
    – Did
    Oct 4 '14 at 20:06















3












$begingroup$


Let $X_n$ be a sequence of random variables.



First, $limsup X_n=inf_nsup_mge nX_m$. So,



$$limsup X_nle c=bigcup_nbigcap_mge nX_mle c$$



Is it correct to say that if $PX_nle c text i.o.equiv PlimsupX_nle c=1$ then $limsup X_nle c text a.s.$?



Edit 1:



By the same way



$$liminf X_nge c=bigcup_nbigcap_mge nX_mge c$$



So, $PX_nge c text i.o.=1 Rightarrow liminf X_nge c text a.s.$



Edit 2:



Following @Did's comments, the answer follows from



$$[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c] text and [X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$$










share|cite|improve this question











$endgroup$











  • $begingroup$
    your question needs repairs.
    $endgroup$
    – drhab
    Oct 4 '14 at 9:40










  • $begingroup$
    @drhab pls explain...
    $endgroup$
    – d.k.o.
    Oct 4 '14 at 9:55










  • $begingroup$
    $Pleft X_ngeq c: i.oright Rightarrow$... How can a value on its own imply something?
    $endgroup$
    – drhab
    Oct 4 '14 at 9:59






  • 2




    $begingroup$
    The third line is wrong. In general, $$limsup X_nle cnebigcup_nbigcap_mge nX_mle c=liminfX_nle c.$$ (I corrected the typo $X_n$ for $X_m$.) It is not even always true that $$limsup X_nle c=limsupX_nle c.$$ For example, if $X_n(omega)=c+1/n$ for every $n$, then $limsup X_n(omega)=lim X_n(omega)=c$ hence $omega$ is in the event $limsup X_nle c$ but $X_n(omega)gt c$ for every $n$ hence $omega$ is neither in the event $limsupX_nle c$ nor in the event $liminfX_nle c$.
    $endgroup$
    – Did
    Oct 4 '14 at 10:36







  • 2




    $begingroup$
    $[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c]$ and $[X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$ $.
    $endgroup$
    – Did
    Oct 4 '14 at 20:06













3












3








3





$begingroup$


Let $X_n$ be a sequence of random variables.



First, $limsup X_n=inf_nsup_mge nX_m$. So,



$$limsup X_nle c=bigcup_nbigcap_mge nX_mle c$$



Is it correct to say that if $PX_nle c text i.o.equiv PlimsupX_nle c=1$ then $limsup X_nle c text a.s.$?



Edit 1:



By the same way



$$liminf X_nge c=bigcup_nbigcap_mge nX_mge c$$



So, $PX_nge c text i.o.=1 Rightarrow liminf X_nge c text a.s.$



Edit 2:



Following @Did's comments, the answer follows from



$$[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c] text and [X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$$










share|cite|improve this question











$endgroup$




Let $X_n$ be a sequence of random variables.



First, $limsup X_n=inf_nsup_mge nX_m$. So,



$$limsup X_nle c=bigcup_nbigcap_mge nX_mle c$$



Is it correct to say that if $PX_nle c text i.o.equiv PlimsupX_nle c=1$ then $limsup X_nle c text a.s.$?



Edit 1:



By the same way



$$liminf X_nge c=bigcup_nbigcap_mge nX_mge c$$



So, $PX_nge c text i.o.=1 Rightarrow liminf X_nge c text a.s.$



Edit 2:



Following @Did's comments, the answer follows from



$$[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c] text and [X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$$







probability-theory random-variables limsup-and-liminf






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 17 '15 at 16:06









BCLC

1




1










asked Oct 4 '14 at 8:22









d.k.o.d.k.o.

10.4k630




10.4k630











  • $begingroup$
    your question needs repairs.
    $endgroup$
    – drhab
    Oct 4 '14 at 9:40










  • $begingroup$
    @drhab pls explain...
    $endgroup$
    – d.k.o.
    Oct 4 '14 at 9:55










  • $begingroup$
    $Pleft X_ngeq c: i.oright Rightarrow$... How can a value on its own imply something?
    $endgroup$
    – drhab
    Oct 4 '14 at 9:59






  • 2




    $begingroup$
    The third line is wrong. In general, $$limsup X_nle cnebigcup_nbigcap_mge nX_mle c=liminfX_nle c.$$ (I corrected the typo $X_n$ for $X_m$.) It is not even always true that $$limsup X_nle c=limsupX_nle c.$$ For example, if $X_n(omega)=c+1/n$ for every $n$, then $limsup X_n(omega)=lim X_n(omega)=c$ hence $omega$ is in the event $limsup X_nle c$ but $X_n(omega)gt c$ for every $n$ hence $omega$ is neither in the event $limsupX_nle c$ nor in the event $liminfX_nle c$.
    $endgroup$
    – Did
    Oct 4 '14 at 10:36







  • 2




    $begingroup$
    $[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c]$ and $[X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$ $.
    $endgroup$
    – Did
    Oct 4 '14 at 20:06
















  • $begingroup$
    your question needs repairs.
    $endgroup$
    – drhab
    Oct 4 '14 at 9:40










  • $begingroup$
    @drhab pls explain...
    $endgroup$
    – d.k.o.
    Oct 4 '14 at 9:55










  • $begingroup$
    $Pleft X_ngeq c: i.oright Rightarrow$... How can a value on its own imply something?
    $endgroup$
    – drhab
    Oct 4 '14 at 9:59






  • 2




    $begingroup$
    The third line is wrong. In general, $$limsup X_nle cnebigcup_nbigcap_mge nX_mle c=liminfX_nle c.$$ (I corrected the typo $X_n$ for $X_m$.) It is not even always true that $$limsup X_nle c=limsupX_nle c.$$ For example, if $X_n(omega)=c+1/n$ for every $n$, then $limsup X_n(omega)=lim X_n(omega)=c$ hence $omega$ is in the event $limsup X_nle c$ but $X_n(omega)gt c$ for every $n$ hence $omega$ is neither in the event $limsupX_nle c$ nor in the event $liminfX_nle c$.
    $endgroup$
    – Did
    Oct 4 '14 at 10:36







  • 2




    $begingroup$
    $[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c]$ and $[X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$ $.
    $endgroup$
    – Did
    Oct 4 '14 at 20:06















$begingroup$
your question needs repairs.
$endgroup$
– drhab
Oct 4 '14 at 9:40




$begingroup$
your question needs repairs.
$endgroup$
– drhab
Oct 4 '14 at 9:40












$begingroup$
@drhab pls explain...
$endgroup$
– d.k.o.
Oct 4 '14 at 9:55




$begingroup$
@drhab pls explain...
$endgroup$
– d.k.o.
Oct 4 '14 at 9:55












$begingroup$
$Pleft X_ngeq c: i.oright Rightarrow$... How can a value on its own imply something?
$endgroup$
– drhab
Oct 4 '14 at 9:59




$begingroup$
$Pleft X_ngeq c: i.oright Rightarrow$... How can a value on its own imply something?
$endgroup$
– drhab
Oct 4 '14 at 9:59




2




2




$begingroup$
The third line is wrong. In general, $$limsup X_nle cnebigcup_nbigcap_mge nX_mle c=liminfX_nle c.$$ (I corrected the typo $X_n$ for $X_m$.) It is not even always true that $$limsup X_nle c=limsupX_nle c.$$ For example, if $X_n(omega)=c+1/n$ for every $n$, then $limsup X_n(omega)=lim X_n(omega)=c$ hence $omega$ is in the event $limsup X_nle c$ but $X_n(omega)gt c$ for every $n$ hence $omega$ is neither in the event $limsupX_nle c$ nor in the event $liminfX_nle c$.
$endgroup$
– Did
Oct 4 '14 at 10:36





$begingroup$
The third line is wrong. In general, $$limsup X_nle cnebigcup_nbigcap_mge nX_mle c=liminfX_nle c.$$ (I corrected the typo $X_n$ for $X_m$.) It is not even always true that $$limsup X_nle c=limsupX_nle c.$$ For example, if $X_n(omega)=c+1/n$ for every $n$, then $limsup X_n(omega)=lim X_n(omega)=c$ hence $omega$ is in the event $limsup X_nle c$ but $X_n(omega)gt c$ for every $n$ hence $omega$ is neither in the event $limsupX_nle c$ nor in the event $liminfX_nle c$.
$endgroup$
– Did
Oct 4 '14 at 10:36





2




2




$begingroup$
$[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c]$ and $[X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$ $.
$endgroup$
– Did
Oct 4 '14 at 20:06




$begingroup$
$[X_ngeqslant c texti.o.]subseteq[limsup X_ngeqslant c]$ and $[X_nleqslant c texti.o.]subseteq[liminf X_nleqslant c]$ $.
$endgroup$
– Did
Oct 4 '14 at 20:06










1 Answer
1






active

oldest

votes


















1












$begingroup$

No.



Let $X_n=left(-1right)^n$ (constant random variables) so that: $$Pleft X_nleq0text i.o.right =1=Pleft X_ngeq0text i.o.right$$



However $limsup X_n=1$ and $liminf X_n=-1$ so that: $$Pleft limsup X_nleq0right =0=Pleft liminf X_ngeq0right$$




addendum:



Let $left(a_nright)$ be some sequence in $mathbbR$.



Then:
$$limsup a_n>cimplies a_n>ctext i.o.implieslimsup a_ngeq c$$






share|cite|improve this answer











$endgroup$












  • $begingroup$
    I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
    $endgroup$
    – rabota
    Mar 16 at 21:09











  • $begingroup$
    @rabota You are correct. Thank you for attending me. I repaired.
    $endgroup$
    – drhab
    Mar 16 at 22:05










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1 Answer
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oldest

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1 Answer
1






active

oldest

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active

oldest

votes






active

oldest

votes









1












$begingroup$

No.



Let $X_n=left(-1right)^n$ (constant random variables) so that: $$Pleft X_nleq0text i.o.right =1=Pleft X_ngeq0text i.o.right$$



However $limsup X_n=1$ and $liminf X_n=-1$ so that: $$Pleft limsup X_nleq0right =0=Pleft liminf X_ngeq0right$$




addendum:



Let $left(a_nright)$ be some sequence in $mathbbR$.



Then:
$$limsup a_n>cimplies a_n>ctext i.o.implieslimsup a_ngeq c$$






share|cite|improve this answer











$endgroup$












  • $begingroup$
    I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
    $endgroup$
    – rabota
    Mar 16 at 21:09











  • $begingroup$
    @rabota You are correct. Thank you for attending me. I repaired.
    $endgroup$
    – drhab
    Mar 16 at 22:05















1












$begingroup$

No.



Let $X_n=left(-1right)^n$ (constant random variables) so that: $$Pleft X_nleq0text i.o.right =1=Pleft X_ngeq0text i.o.right$$



However $limsup X_n=1$ and $liminf X_n=-1$ so that: $$Pleft limsup X_nleq0right =0=Pleft liminf X_ngeq0right$$




addendum:



Let $left(a_nright)$ be some sequence in $mathbbR$.



Then:
$$limsup a_n>cimplies a_n>ctext i.o.implieslimsup a_ngeq c$$






share|cite|improve this answer











$endgroup$












  • $begingroup$
    I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
    $endgroup$
    – rabota
    Mar 16 at 21:09











  • $begingroup$
    @rabota You are correct. Thank you for attending me. I repaired.
    $endgroup$
    – drhab
    Mar 16 at 22:05













1












1








1





$begingroup$

No.



Let $X_n=left(-1right)^n$ (constant random variables) so that: $$Pleft X_nleq0text i.o.right =1=Pleft X_ngeq0text i.o.right$$



However $limsup X_n=1$ and $liminf X_n=-1$ so that: $$Pleft limsup X_nleq0right =0=Pleft liminf X_ngeq0right$$




addendum:



Let $left(a_nright)$ be some sequence in $mathbbR$.



Then:
$$limsup a_n>cimplies a_n>ctext i.o.implieslimsup a_ngeq c$$






share|cite|improve this answer











$endgroup$



No.



Let $X_n=left(-1right)^n$ (constant random variables) so that: $$Pleft X_nleq0text i.o.right =1=Pleft X_ngeq0text i.o.right$$



However $limsup X_n=1$ and $liminf X_n=-1$ so that: $$Pleft limsup X_nleq0right =0=Pleft liminf X_ngeq0right$$




addendum:



Let $left(a_nright)$ be some sequence in $mathbbR$.



Then:
$$limsup a_n>cimplies a_n>ctext i.o.implieslimsup a_ngeq c$$







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Mar 16 at 22:04

























answered Oct 4 '14 at 10:12









drhabdrhab

103k545136




103k545136











  • $begingroup$
    I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
    $endgroup$
    – rabota
    Mar 16 at 21:09











  • $begingroup$
    @rabota You are correct. Thank you for attending me. I repaired.
    $endgroup$
    – drhab
    Mar 16 at 22:05
















  • $begingroup$
    I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
    $endgroup$
    – rabota
    Mar 16 at 21:09











  • $begingroup$
    @rabota You are correct. Thank you for attending me. I repaired.
    $endgroup$
    – drhab
    Mar 16 at 22:05















$begingroup$
I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
$endgroup$
– rabota
Mar 16 at 21:09





$begingroup$
I think you made a mistake in the addendum. We have $1/n >0$ infinitely often, yet $limsup 1/n = 0$.
$endgroup$
– rabota
Mar 16 at 21:09













$begingroup$
@rabota You are correct. Thank you for attending me. I repaired.
$endgroup$
– drhab
Mar 16 at 22:05




$begingroup$
@rabota You are correct. Thank you for attending me. I repaired.
$endgroup$
– drhab
Mar 16 at 22:05

















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