Independent Events Math Example 1

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Example 1

easy
A fair coin is flipped and a fair die is rolled. Find P(Heads and a 4)P(\text{Heads and a 4}).

Solution

  1. 1
    Identify the two events: A=HeadsA = \text{Heads}, B=rolling a 4B = \text{rolling a 4}
  2. 2
    Check independence: the coin flip does not affect the die roll, so AA and BB are independent
  3. 3
    Find individual probabilities: P(A)=12P(A) = \frac{1}{2}, P(B)=16P(B) = \frac{1}{6}
  4. 4
    Apply multiplication rule: P(AB)=P(A)P(B)=1216=112P(A \cap B) = P(A) \cdot P(B) = \frac{1}{2} \cdot \frac{1}{6} = \frac{1}{12}

Answer

P(Heads and a 4)=112P(\text{Heads and a 4}) = \frac{1}{12}
Two events are independent if the occurrence of one does not change the probability of the other. For independent events, P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B). Physical separation of experiments is the clearest indicator of independence.

About Independent Events

Two events are independent if the occurrence of one does not change the probability of the other: P(AB)=P(A)P(B)P(A \cap B) = P(A) \cdot P(B).

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