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If 
P(B)=0.55,P(A∣B)=0.80,P(B^('))=0.45, and 
P(A∣B^('))=0.40, find 
P(B∣A)

If P(B)=0.55,P(AB)=0.80,P(B)=0.45 P(B)=0.55, P(A \mid B)=0.80, P\left(B^{\prime}\right)=0.45 , and P(AB)=0.40 P\left(A \mid B^{\prime}\right)=0.40 , find P(BA) P(B \mid A)

Full solution

Q. If P(B)=0.55,P(AB)=0.80,P(B)=0.45 P(B)=0.55, P(A \mid B)=0.80, P\left(B^{\prime}\right)=0.45 , and P(AB)=0.40 P\left(A \mid B^{\prime}\right)=0.40 , find P(BA) P(B \mid A)
  1. Rephrase Problem: First, let's rephrase the "Find the conditional probability P(BA)P(B|A)."
  2. Apply Bayes' Theorem: To find P(BA)P(B|A), we will use Bayes' theorem, which states that P(BA)=P(AB)P(B)P(A)P(B|A) = \frac{P(A|B) \cdot P(B)}{P(A)}.
  3. Calculate P(A)P(A): We already have P(AB)=0.80P(A|B) = 0.80 and P(B)=0.55P(B) = 0.55. We need to find P(A)P(A), which is the total probability of AA occurring.
  4. Use Law of Total Probability: To find P(A)P(A), we use the law of total probability: P(A)=P(AB)P(B)+P(AB)P(B)P(A) = P(A|B) \cdot P(B) + P(A|B') \cdot P(B').
  5. Calculate P(A)P(A): We have P(AB)=0.80P(A|B) = 0.80, P(B)=0.55P(B) = 0.55, P(AB)=0.40P(A|B') = 0.40, and P(B)=0.45P(B') = 0.45. Let's calculate P(A)P(A).\newlineP(A)=(0.80×0.55)+(0.40×0.45)P(A) = (0.80 \times 0.55) + (0.40 \times 0.45)\newlineP(A)=0.44+0.18P(A) = 0.44 + 0.18\newlineP(A)=0.62P(A) = 0.62
  6. Calculate P(BA)P(B|A): Now we can calculate P(BA)P(B|A) using Bayes' theorem.\newlineP(BA)=P(AB)P(B)P(A)P(B|A) = \frac{P(A|B) \cdot P(B)}{P(A)}\newlineP(BA)=(0.800.55)0.62P(B|A) = \frac{(0.80 \cdot 0.55)}{0.62}\newlineP(BA)=0.440.62P(B|A) = \frac{0.44}{0.62}
  7. Simplify Fraction: Finally, we simplify the fraction to get the value of P(BA)P(B|A).P(BA)=0.440.620.7097P(B|A) = \frac{0.44}{0.62} \approx 0.7097

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