Math Problem Statement

Given Venn Diagrams and a two-way table, determine whether A and B are dependent or independent. Calculate various probabilities (P(A), P(B|A), P(A ∪ B), P(A ∩ B)).

Solution

Let's work through the problems based on the image you provided. I'll begin by interpreting and solving each part of the questions related to the Venn diagrams and the table provided.

1. First Venn Diagram (30 total outcomes)

  • A=15A = 15, AB=5A \cap B = 5, B=10B = 10, total outcomes = 30.

a. Are AA and BB dependent or independent? Why?

  • To determine whether AA and BB are independent, we check if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B).

Let's calculate:

  • P(A)=15+530=2030=23P(A) = \frac{15 + 5}{30} = \frac{20}{30} = \frac{2}{3}
  • P(B)=10+530=1530=12P(B) = \frac{10 + 5}{30} = \frac{15}{30} = \frac{1}{2}
  • P(AB)=530=16P(A \cap B) = \frac{5}{30} = \frac{1}{6}

Now, check if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B):

  • P(A)P(B)=2312=13P(A) \cdot P(B) = \frac{2}{3} \cdot \frac{1}{2} = \frac{1}{3}
  • Since 1613\frac{1}{6} \neq \frac{1}{3}, AA and BB are dependent.

b. P(A)P(A)

P(A)=2030=23P(A) = \frac{20}{30} = \frac{2}{3}.

c. P(BA)P(B|A)

P(BA)=P(AB)P(A)=5302030=520=14P(B|A) = \frac{P(A \cap B)}{P(A)} = \frac{\frac{5}{30}}{\frac{20}{30}} = \frac{5}{20} = \frac{1}{4}.

d. P(AB)P(A \cup B)

P(AB)=P(A)+P(B)P(AB)=23+1216=46+3616=66=1P(A \cup B) = P(A) + P(B) - P(A \cap B) = \frac{2}{3} + \frac{1}{2} - \frac{1}{6} = \frac{4}{6} + \frac{3}{6} - \frac{1}{6} = \frac{6}{6} = 1.

e. P(AB)P(A \cap B)

P(AB)=530=16P(A \cap B) = \frac{5}{30} = \frac{1}{6}.

2. Second Venn Diagram (32 total outcomes)

  • A=8A = 8, AB=2A \cap B = 2, B=16B = 16, total outcomes = 32.

a. Are AA and BB dependent or independent? Why?

Let's calculate:

  • P(A)=8+232=1032=516P(A) = \frac{8 + 2}{32} = \frac{10}{32} = \frac{5}{16}
  • P(B)=16+232=1832=916P(B) = \frac{16 + 2}{32} = \frac{18}{32} = \frac{9}{16}
  • P(AB)=232=116P(A \cap B) = \frac{2}{32} = \frac{1}{16}

Now, check if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B):

  • P(A)P(B)=516916=45256P(A) \cdot P(B) = \frac{5}{16} \cdot \frac{9}{16} = \frac{45}{256}
  • P(AB)=116=16256P(A \cap B) = \frac{1}{16} = \frac{16}{256}
  • Since 4525616256\frac{45}{256} \neq \frac{16}{256}, AA and BB are dependent.

b. P(B)P(B)

P(B)=1832=916P(B) = \frac{18}{32} = \frac{9}{16}.

c. P(AB)P(A|B)

P(AB)=P(AB)P(B)=2321832=218=19P(A|B) = \frac{P(A \cap B)}{P(B)} = \frac{\frac{2}{32}}{\frac{18}{32}} = \frac{2}{18} = \frac{1}{9}.

d. P(AB)P(A \cup B)

P(AB)=P(A)+P(B)P(AB)=516+916116=1316P(A \cup B) = P(A) + P(B) - P(A \cap B) = \frac{5}{16} + \frac{9}{16} - \frac{1}{16} = \frac{13}{16}.

e. P(AB)P(A \cap B)

P(AB)=232=116P(A \cap B) = \frac{2}{32} = \frac{1}{16}.

3. Two-way Table (200 total outcomes)

a. Are AA and BB dependent or independent? Why?

To determine dependence, use the formula P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B).

  • P(A)=65200=0.325P(A) = \frac{65}{200} = 0.325
  • P(B)=100200=0.5P(B) = \frac{100}{200} = 0.5
  • P(AB)=25200=0.125P(A \cap B) = \frac{25}{200} = 0.125

Now, check if P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B):

  • P(A)P(B)=0.3250.5=0.1625P(A) \cdot P(B) = 0.325 \cdot 0.5 = 0.1625
  • Since 0.1250.16250.125 \neq 0.1625, AA and BB are dependent.

Would you like further clarification or details on any part? Here are some related questions to deepen your understanding:

  1. How do we determine whether events are independent in probability theory?
  2. Can you explain why the intersection P(AB)P(A \cap B) is important in determining dependence?
  3. What is the significance of conditional probability P(BA)P(B|A)?
  4. How does the union formula P(AB)P(A \cup B) help in understanding combined probabilities?
  5. What would change if AA and BB were independent events?

Tip: Always compare P(AB)P(A \cap B) with P(A)P(B)P(A) \cdot P(B) to quickly check for independence.

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Math Problem Analysis

Mathematical Concepts

Probability
Venn Diagrams
Dependent and Independent Events

Formulas

P(A ∩ B) = P(A) · P(B) (for independent events)
P(A ∪ B) = P(A) + P(B) - P(A ∩ B)
Conditional Probability: P(B|A) = P(A ∩ B) / P(A)

Theorems

Law of Total Probability
Independence of Events

Suitable Grade Level

Grades 9-12