Explanation
1. Definition of Conditional Probability
The formula for conditional probability of an event X given Y is:
Applying this to our specific case:
2. Property of Independent Events
If A and B are independent events, then their complements Aˉ and Bˉ are also independent. This is a fundamental theorem in probability.
Because they are independent, the probability of their intersection is the product of their individual probabilities:
3. Substitution and Simplification
Now, substitute the intersection from Step 2 back into the formula from Step 1:
P(Aˉ∣Bˉ)=P(Bˉ)P(Aˉ)⋅P(Bˉ)
The P(Bˉ) terms in the numerator and denominator cancel out (assuming P(Bˉ)=0):
4. Alternative Forms
Since P(Aˉ)=1−P(A), the answer can also be written as: