Math Problem Statement

The Venn diagram shows the probabilities of three events A, B, and C. Find: a) P(A | B), b) P(C | A'), c) P(A ∩ B | C^c), d) P(C | A' ∪ B')

Solution

The problem provides a Venn diagram that displays the probabilities of three events, AA, BB, and CC, along with several related probability questions. I'll break it down and solve each part:

The information in the Venn diagram:

  • P(ABC)=0.1P(A \cap B \cap C) = 0.1
  • P(ABCc)=0.08P(A \cap B \cap C^c) = 0.08 (where CcC^c is the complement of CC)
  • P(ABcC)=0.05P(A \cap B^c \cap C) = 0.05
  • P(AcBC)=0.12P(A^c \cap B \cap C) = 0.12
  • P(ABcCc)=0.2P(A \cap B^c \cap C^c) = 0.2
  • P(AcBCc)=0.1P(A^c \cap B \cap C^c) = 0.1
  • P(AcBcC)=0.15P(A^c \cap B^c \cap C) = 0.15

Now let's solve the questions:

(a) P(AB)P(A | B)

This is the conditional probability of AA given BB, calculated as:

P(AB)=P(AB)P(B)P(A | B) = \frac{P(A \cap B)}{P(B)}

From the diagram:

  • P(AB)=P(ABC)+P(ABCc)=0.1+0.08=0.18P(A \cap B) = P(A \cap B \cap C) + P(A \cap B \cap C^c) = 0.1 + 0.08 = 0.18
  • P(B)=P(AB)+P(AcBC)+P(AcBCc)=0.18+0.12+0.1=0.4P(B) = P(A \cap B) + P(A^c \cap B \cap C) + P(A^c \cap B \cap C^c) = 0.18 + 0.12 + 0.1 = 0.4

Thus:

P(AB)=0.180.4=0.45P(A | B) = \frac{0.18}{0.4} = 0.45

(b) P(CA)P(C | A')

This is the conditional probability of CC given AA' (the complement of AA):

P(CA)=P(CA)P(A)P(C | A') = \frac{P(C \cap A')}{P(A')}

From the diagram:

  • P(CA)=P(AcBC)+P(AcBcC)=0.12+0.15=0.27P(C \cap A') = P(A^c \cap B \cap C) + P(A^c \cap B^c \cap C) = 0.12 + 0.15 = 0.27
  • P(A)=1P(A)=1(0.2+0.1+0.05+0.08+0.1)=10.53=0.47P(A') = 1 - P(A) = 1 - (0.2 + 0.1 + 0.05 + 0.08 + 0.1) = 1 - 0.53 = 0.47

Thus:

P(CA)=0.270.470.574P(C | A') = \frac{0.27}{0.47} \approx 0.574

(c) P(ABCc)P(A \cap B | C^c)

This is the conditional probability of ABA \cap B given CcC^c (the complement of CC):

P(ABCc)=P(ABCc)P(Cc)P(A \cap B | C^c) = \frac{P(A \cap B \cap C^c)}{P(C^c)}

From the diagram:

  • P(ABCc)=0.08P(A \cap B \cap C^c) = 0.08
  • P(Cc)=1P(C)=1(0.1+0.05+0.12+0.15)=10.42=0.58P(C^c) = 1 - P(C) = 1 - (0.1 + 0.05 + 0.12 + 0.15) = 1 - 0.42 = 0.58

Thus:

P(ABCc)=0.080.580.138P(A \cap B | C^c) = \frac{0.08}{0.58} \approx 0.138

(d) P(CAB)P(C | A' \cup B')

This is the conditional probability of CC given ABA' \cup B' (the union of the complements of AA and BB):

P(CAB)=P(C(AB))P(AB)P(C | A' \cup B') = \frac{P(C \cap (A' \cup B'))}{P(A' \cup B')}

First, calculate P(AB)P(A' \cup B'):

  • ABA' \cup B' covers all regions outside of ABA \cap B, i.e., it includes AcBCA^c \cap B \cap C, AcBCcA^c \cap B \cap C^c, AcBcCA^c \cap B^c \cap C, and AcBcCcA^c \cap B^c \cap C^c.

So, we have: P(AB)=0.12+0.1+0.15+0.2=0.57P(A' \cup B') = 0.12 + 0.1 + 0.15 + 0.2 = 0.57

Now, calculate P(C(AB))P(C \cap (A' \cup B')):

  • This includes the regions AcBCA^c \cap B \cap C and AcBcCA^c \cap B^c \cap C, so: P(C(AB))=0.12+0.15=0.27P(C \cap (A' \cup B')) = 0.12 + 0.15 = 0.27

Thus:

P(CAB)=0.270.570.474P(C | A' \cup B') = \frac{0.27}{0.57} \approx 0.474


Let me know if you'd like further details or clarifications on any part.

Related Questions:

  1. How do we find the complement of a set in probability?
  2. What are the different ways to compute the union of events in probability?
  3. Can you explain the concept of conditional probability with a simple example?
  4. How do independent and mutually exclusive events differ in probability?
  5. What is the significance of the intersection of sets in probability?

Tip:

In conditional probability, always ensure the denominator reflects the total probability of the condition being true.

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Math Problem Analysis

Mathematical Concepts

Probability
Venn Diagrams
Conditional Probability
Set Theory

Formulas

P(A | B) = P(A ∩ B) / P(B)
P(C | A') = P(C ∩ A') / P(A')
P(A ∩ B | C^c) = P(A ∩ B ∩ C^c) / P(C^c)
P(C | A' ∪ B') = P(C ∩ (A' ∪ B')) / P(A' ∪ B')

Theorems

Conditional Probability Theorem
Union and Intersection of Sets

Suitable Grade Level

Grades 10-12