SOLUTION: Determine all joint probabilities listed below from the following information: P(A)=0.74,P(Ac)=0.26,P(B|A)=0.43,P(B|Ac)=0.65 P(A and B) = P(A and Bc) = P(Ac and B) = P(

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Question 1147684: Determine all joint probabilities listed below from the following information:
P(A)=0.74,P(Ac)=0.26,P(B|A)=0.43,P(B|Ac)=0.65
P(A and B) =
P(A and Bc) =
P(Ac and B) =
P(Ac and Bc) =

Found 3 solutions by Edwin McCravy, AnlytcPhil, ikleyn:
Answer by Edwin McCravy(20064)   (Show Source): You can put this solution on YOUR website!
Below is the final solution.

Edwin AKA AnlytcPhil

Answer by AnlytcPhil(1809)   (Show Source): You can put this solution on YOUR website!
let w, x, y, and z represent the probabilities of the regions
they are in in the Venn diagram below



P(A and B) = "what's in both circles" = x
P(A and Cc) = "what's in A but not in B" = w,
P(Ac and B) = "what's not in A but is in B" = y,
P(Ac and Bc) = "what's not in A and not in B" = z



Simplifying the third and fourth equations:

    

We have this system:



Solve the system:



and get w = 0.4218, x = 0.3182

Solve the system:



and get y = 0.169, x = 0.091

Put those values in the Venn diagram:



Edwin

Answer by ikleyn(52884)   (Show Source): You can put this solution on YOUR website!
.

(1)  To calculate P(A and B), it is enough to have these two given values  P(A)= 0.74  and  P(B | A)= 0.43.


     By the definition of the conditional probability,  P(B | A) = P(A and B)/P(A).


     Therefore, to get P(A and B), simply multiply P(A | B) and P(A) to get


                P(A and B) = 0.74*0.43 = 0.3182.     ANSWER




(2)  P(A and Bc) = P(A) - P(A and B) = 0.74 - 0.3182 = 0.4218.    ANSWER




(3)  The solution for (3) is absolutely identical to the solution for (1).

     Therefore, I will repeat it word-in-word.



     To calculate P(Ac and B), it is enough to have these two given values  P(Ac)= 0.26  and  P(B | Ac)= 0.65.


     By the definition of the conditional probability,  P(B | Ac) = P(B and Ac)/P(Ac).


     Therefore, to get P(Ac and B), simply multiply P(B | Ac) and P(Ac) to get


                P(Ac and B) = 0.65*0.26 = 0.169.     ANSWER




(4)  P(Ac and Bc) = P(Ac) - P(Ac and B) = 0.26 - 0.169 = 0.091.    ANSWER


Solved.

------------

Thus, to solve the problem

    - you don't need to use and to plot Venn diagram;

    - you do not need to form and to solve the system/systems of linear equations.

All you need is to know the basic definitions and properties of probabilities  (and of conditional probability,  in particular).


In this context,  the Edwin' solution  leads you to  NOWHERE.

This problem is of introductory level on conditional probability, and the solution technique must be adequate.

I am 200% sure that this problem was designed,  created,  intended and expected to be solved by the method of my post.

I write it to you not for making a war with Edwin, but with the unique goal to show you the correct way solving such problems.


/\/\/\/\/\/\/\/

On conditional probabilities, see the lesson
    - Conditional probability problems
in this site.


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