Math Problem Statement

Let A and B be events with specific probabilities (P(A), P(B), P(A ∩ B), P(A ∪ B)). Determine if A and B are independent or mutually exclusive, and compute the necessary probabilities.

Solution

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Problem 1:

Let AA and BB be events with P(A)=0.6P(A) = 0.6, P(B)=0.9P(B) = 0.9, and P(AB)=0.5P(A \cap B) = 0.5.

(a) Are AA and BB independent? Explain.
Two events are independent if: P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B) Let's check this condition: P(A)P(B)=0.60.9=0.54P(A) \cdot P(B) = 0.6 \cdot 0.9 = 0.54 Since P(AB)=0.5P(A \cap B) = 0.5 and 0.540.50.54 \neq 0.5, the events AA and BB are not independent.

(b) Compute P(AB)P(A \cup B).
We use the formula for the union of two events: P(AB)=P(A)+P(B)P(AB)P(A \cup B) = P(A) + P(B) - P(A \cap B) Substitute the given values: P(AB)=0.6+0.90.5=1.0P(A \cup B) = 0.6 + 0.9 - 0.5 = 1.0

(c) Are AA and BB mutually exclusive? Explain.
Two events are mutually exclusive if: P(AB)=0P(A \cap B) = 0 Since P(AB)=0.50P(A \cap B) = 0.5 \neq 0, the events AA and BB are not mutually exclusive.


Problem 2:

Let AA and BB be events with P(A)=0.4P(A) = 0.4, P(B)=0.5P(B) = 0.5, and P(AB)=0.6P(A \cup B) = 0.6.

(a) Compute P(AB)P(A \cap B).
We use the same formula for the union of two events: P(AB)=P(A)+P(B)P(AB)P(A \cup B) = P(A) + P(B) - P(A \cap B) Substitute the known values: 0.6=0.4+0.5P(AB)0.6 = 0.4 + 0.5 - P(A \cap B) P(AB)=0.90.6=0.3P(A \cap B) = 0.9 - 0.6 = 0.3

(b) Are AA and BB mutually exclusive? Explain.
Since P(AB)=0.30P(A \cap B) = 0.3 \neq 0, the events AA and BB are not mutually exclusive.

(c) Are AA and BB independent? Explain.
Check if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B): P(A)P(B)=0.40.5=0.2P(A) \cdot P(B) = 0.4 \cdot 0.5 = 0.2 Since P(AB)=0.30.2P(A \cap B) = 0.3 \neq 0.2, the events AA and BB are not independent.


Problem 3:

Let AA and BB be events with P(A)=0.5P(A) = 0.5, P(B)=0.3P(B) = 0.3, and P(AB)=0.8P(A \cup B) = 0.8.

(a) Compute P(AB)P(A \cap B).
Using the formula for the union of two events: P(AB)=P(A)+P(B)P(AB)P(A \cup B) = P(A) + P(B) - P(A \cap B) Substitute the known values: 0.8=0.5+0.3P(AB)0.8 = 0.5 + 0.3 - P(A \cap B) P(AB)=0.80.8=0P(A \cap B) = 0.8 - 0.8 = 0

(b) Are AA and BB mutually exclusive? Explain.
Since P(AB)=0P(A \cap B) = 0, the events AA and BB are mutually exclusive.

(c) Are AA and BB independent? Explain.
For independence, we check if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B). Since P(AB)=0P(A \cap B) = 0 and P(A)P(B)=0.50.3=0.15P(A) \cdot P(B) = 0.5 \cdot 0.3 = 0.15, they are not independent because 00.150 \neq 0.15.


Do you want more details or have any questions?

Related Questions:

  1. What is the difference between mutually exclusive and independent events?
  2. How do you compute P(AB)P(A \cup B) if AA and BB are mutually exclusive?
  3. Can two events be both mutually exclusive and independent? Why or why not?
  4. How would the answers change if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B)?
  5. What are some real-world examples of independent and mutually exclusive events?

Tip:

Always start by checking if events are mutually exclusive or independent before calculating probabilities, as this affects the formulas you'll use.

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Math Problem Analysis

Mathematical Concepts

Probability
Set Theory
Union and Intersection of Events
Mutual Exclusivity
Independence of Events

Formulas

P(A ∪ B) = P(A) + P(B) - P(A ∩ B)
Independence condition: P(A ∩ B) = P(A) × P(B)
Mutually exclusive condition: P(A ∩ B) = 0

Theorems

Addition Rule for Probabilities
Conditions for Independent Events
Conditions for Mutually Exclusive Events

Suitable Grade Level

Grades 10-12