Joint probabilities of $A$ and independent $B$ and $C$












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Given that $B$ and $C$ are independent, when would $$P(Acap Bcap C) = P(Acap B)P(Acap C);?$$











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  • 1




    $begingroup$
    A, B, C are three events or logical statements. comma represents logical and or conjunction. P(X) represents probability that statement X is true.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:42












  • $begingroup$
    Probably it requires that B and C never happen at the same time. If that is the case, the intersection of A, B, and C is same as the union of the (intersection of A and B) and the (intersection of B and C). wait... my brain is not working today.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:51








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    $begingroup$
    That would require either $B$ or $C$ to be impossible.
    $endgroup$
    – copper.hat
    Dec 31 '18 at 19:53
















1












$begingroup$



Given that $B$ and $C$ are independent, when would $$P(Acap Bcap C) = P(Acap B)P(Acap C);?$$











share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    A, B, C are three events or logical statements. comma represents logical and or conjunction. P(X) represents probability that statement X is true.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:42












  • $begingroup$
    Probably it requires that B and C never happen at the same time. If that is the case, the intersection of A, B, and C is same as the union of the (intersection of A and B) and the (intersection of B and C). wait... my brain is not working today.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:51








  • 1




    $begingroup$
    That would require either $B$ or $C$ to be impossible.
    $endgroup$
    – copper.hat
    Dec 31 '18 at 19:53














1












1








1





$begingroup$



Given that $B$ and $C$ are independent, when would $$P(Acap Bcap C) = P(Acap B)P(Acap C);?$$











share|cite|improve this question











$endgroup$





Given that $B$ and $C$ are independent, when would $$P(Acap Bcap C) = P(Acap B)P(Acap C);?$$








probability






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edited Dec 31 '18 at 21:18









greedoid

39k114797




39k114797










asked Dec 31 '18 at 19:40









hamster on wheelshamster on wheels

1155




1155








  • 1




    $begingroup$
    A, B, C are three events or logical statements. comma represents logical and or conjunction. P(X) represents probability that statement X is true.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:42












  • $begingroup$
    Probably it requires that B and C never happen at the same time. If that is the case, the intersection of A, B, and C is same as the union of the (intersection of A and B) and the (intersection of B and C). wait... my brain is not working today.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:51








  • 1




    $begingroup$
    That would require either $B$ or $C$ to be impossible.
    $endgroup$
    – copper.hat
    Dec 31 '18 at 19:53














  • 1




    $begingroup$
    A, B, C are three events or logical statements. comma represents logical and or conjunction. P(X) represents probability that statement X is true.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:42












  • $begingroup$
    Probably it requires that B and C never happen at the same time. If that is the case, the intersection of A, B, and C is same as the union of the (intersection of A and B) and the (intersection of B and C). wait... my brain is not working today.
    $endgroup$
    – hamster on wheels
    Dec 31 '18 at 19:51








  • 1




    $begingroup$
    That would require either $B$ or $C$ to be impossible.
    $endgroup$
    – copper.hat
    Dec 31 '18 at 19:53








1




1




$begingroup$
A, B, C are three events or logical statements. comma represents logical and or conjunction. P(X) represents probability that statement X is true.
$endgroup$
– hamster on wheels
Dec 31 '18 at 19:42






$begingroup$
A, B, C are three events or logical statements. comma represents logical and or conjunction. P(X) represents probability that statement X is true.
$endgroup$
– hamster on wheels
Dec 31 '18 at 19:42














$begingroup$
Probably it requires that B and C never happen at the same time. If that is the case, the intersection of A, B, and C is same as the union of the (intersection of A and B) and the (intersection of B and C). wait... my brain is not working today.
$endgroup$
– hamster on wheels
Dec 31 '18 at 19:51






$begingroup$
Probably it requires that B and C never happen at the same time. If that is the case, the intersection of A, B, and C is same as the union of the (intersection of A and B) and the (intersection of B and C). wait... my brain is not working today.
$endgroup$
– hamster on wheels
Dec 31 '18 at 19:51






1




1




$begingroup$
That would require either $B$ or $C$ to be impossible.
$endgroup$
– copper.hat
Dec 31 '18 at 19:53




$begingroup$
That would require either $B$ or $C$ to be impossible.
$endgroup$
– copper.hat
Dec 31 '18 at 19:53










1 Answer
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$begingroup$

We have



$$P(Acap Bcap C) = P(Bcap C)P(A|Bcap C) = P(B)P(C)P(A|Bcap C) $$
Since $$ P(Acap B)P(Acap C) = P(B)P(A|B)P(C)P(A|C)$$
we get $$boxed{P(A|Bcap C) = P(A|B)P(A|C)}$$






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    $begingroup$

    We have



    $$P(Acap Bcap C) = P(Bcap C)P(A|Bcap C) = P(B)P(C)P(A|Bcap C) $$
    Since $$ P(Acap B)P(Acap C) = P(B)P(A|B)P(C)P(A|C)$$
    we get $$boxed{P(A|Bcap C) = P(A|B)P(A|C)}$$






    share|cite|improve this answer











    $endgroup$


















      1












      $begingroup$

      We have



      $$P(Acap Bcap C) = P(Bcap C)P(A|Bcap C) = P(B)P(C)P(A|Bcap C) $$
      Since $$ P(Acap B)P(Acap C) = P(B)P(A|B)P(C)P(A|C)$$
      we get $$boxed{P(A|Bcap C) = P(A|B)P(A|C)}$$






      share|cite|improve this answer











      $endgroup$
















        1












        1








        1





        $begingroup$

        We have



        $$P(Acap Bcap C) = P(Bcap C)P(A|Bcap C) = P(B)P(C)P(A|Bcap C) $$
        Since $$ P(Acap B)P(Acap C) = P(B)P(A|B)P(C)P(A|C)$$
        we get $$boxed{P(A|Bcap C) = P(A|B)P(A|C)}$$






        share|cite|improve this answer











        $endgroup$



        We have



        $$P(Acap Bcap C) = P(Bcap C)P(A|Bcap C) = P(B)P(C)P(A|Bcap C) $$
        Since $$ P(Acap B)P(Acap C) = P(B)P(A|B)P(C)P(A|C)$$
        we get $$boxed{P(A|Bcap C) = P(A|B)P(A|C)}$$







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Dec 31 '18 at 21:02

























        answered Dec 31 '18 at 20:56









        greedoidgreedoid

        39k114797




        39k114797






























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