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Homework Help: Probability problem

  1. Nov 19, 2014 #1

    chwala

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    Gold Member

    1. The problem statement, all variables and given/known data ## The question is as follows given ##P(A/B)=0.8, P(B/A")=0.6## and P(A)=0.75 then find P(B) and ## P(A/B)##


    2. Relevant equations


    3. The attempt at a solution
    ##P(A/B)= P(AnB)/P(B) ## where## P(AnB)= P(B/A).P(A)= 0.8*0.75=0.6##
    ##P(A/B)= 0.6/P(B)## am now stuck here how do i move from here?
     
  2. jcsd
  3. Nov 19, 2014 #2
    looks like you're nearly there... calculate ## p(A') ##, then can you find ## p(A' \land B)## ?
     
  4. Nov 19, 2014 #3

    statdad

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    If you are given [itex] P(A \mid B) [/itex] why do you need to calculate it?

    To be clear: are these the items you are given and the items you are to find?
    [tex]
    \begin{align*}
    P(A \mid B) & = 0.8 \\
    P(B \mid A') & = 0.6 \\
    P(A) & = 0.75 \\
    \text{Need} & \\
    P(B) & \\
    P(A \cap B) \text{ (instead of } & P(A \mid B) \text{?)}
    \end{align*}
    [/tex]
     
  5. Nov 20, 2014 #4

    chwala

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    sorry the terms given are P(B/A)= 0.8 , P(B/A")=0.6 and P(A)=0.75 I need to find P(A/B) and P(B)
     
  6. Nov 21, 2014 #5

    statdad

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    Homework Helper

    Well, if you have [itex] P(B \mid A) [/itex] and [itex] P(A) [/itex] you can calculate [itex] P(A \cap B) [/itex] . You can also find [itex] P(A') [/itex] and
    then get [itex] P(A' \cap B) [/itex]. What will [itex] P(A \cap B) [/itex] and [itex] P(A' \cap B) [/itex] together get you? Once you have that you can finish the questions.
     
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