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November 08, 2025, 05:07:29 am
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Author Topic: Probability  (Read 1195 times)  Share 

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chuckjefster90

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Probability
« on: September 27, 2009, 05:34:51 pm »
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A gambler has two coints. A and B. THe probabilities of their turning up heads are 0.8 and .4 respectively. One coin is selected at random and tossed twice and a head and a tail are observed. Find the probability that coin A was selected

Helps plz
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kamil9876

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Re: Probability
« Reply #1 on: September 27, 2009, 05:59:37 pm »
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Find the probabilities of AHT,ATH,BTH,BHT



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Voltaire: "There is an astonishing imagination even in the science of mathematics ... We repeat, there is far more imagination in the head of Archimedes than in that of Homer."

chuckjefster90

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Re: Probability
« Reply #2 on: September 27, 2009, 06:20:45 pm »
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kool thanks

also got another prob

Pr(a)=1/2
pr(b)=1/4
Pr(a given b)=1/6

How do u find Pr(a' given B)
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Flaming_Arrow

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Re: Probability
« Reply #3 on: September 27, 2009, 06:38:48 pm »
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Pr(A n B) = Pr(A|B) * Pr(B) = 1/24

Pr(A' n B) = Pr(B)- Pr(A n B) = 5/24

Pr(A'|B) = Pr(A' n B)/ Pr(B) = 5/6
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chuckjefster90

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Re: Probability
« Reply #4 on: September 27, 2009, 09:06:52 pm »
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uhm i dnt get wat this Pr(A' n B) = Pr(B)- Pr(A n B) = 5/24 means and where u got that from?
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TrueTears

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Re: Probability
« Reply #5 on: September 27, 2009, 09:07:57 pm »
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Draw a venn diagram.
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chuckjefster90

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Re: Probability
« Reply #6 on: September 27, 2009, 09:37:47 pm »
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how come pr(a') isnt 1-pr(a)?
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TrueTears

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Re: Probability
« Reply #7 on: September 27, 2009, 09:38:31 pm »
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It is.
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PhD @ MIT (Economics).

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chuckjefster90

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Re: Probability
« Reply #8 on: September 27, 2009, 09:40:26 pm »
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but for this question? i drew the venn diagram and im still stuck

helps  :(
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TrueTears

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Re: Probability
« Reply #9 on: September 27, 2009, 09:42:33 pm »
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What FA said: Pr(A' n B) = Pr(B)- Pr(A n B)

If you get B minus the intersection of A and B then you get A' n B.

The Venn diagram tells you this straight away if you drew it right.
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Flaming_Arrow

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Re: Probability
« Reply #10 on: September 27, 2009, 10:17:45 pm »
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soz for the shit drawing, can't find laptop mouse had to use touchpad
« Last Edit: September 27, 2009, 10:19:31 pm by Flaming_Arrow »
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chuckjefster90

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Re: Probability
« Reply #11 on: September 27, 2009, 10:28:29 pm »
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THANKS SOO MUCH I GET IT NOW!
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