# S1 Probability Formulas

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• Created by: Phoebe
• Created on: 05-10-13 20:42
P(A u B) = P(A) + P(B) - P(A n B) OR P(A n B) = P(A) + P(B) - P(A u B)
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Conditional Probability
P(A n B) = P(A n B) / P(A) ∴ P(A|B) = P(A n B) / P(B)
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Multiplication Law
P(A n B) = P(B|A) x P(A) OR P(A n B) = P(A|B) x P(B)
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Mutually Exclusive
P(A or B) = P(A) + P(B) -- P(A n B) = 0
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Multiplication Law for INDEPENDENT EVENTS
P(A n B) = P(A) x P(B) -> P(A|B) = P(A) = P(AnB) = P(A) P(B)
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Another useful formula
P(A) = P(A n B) + P(A n B')
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Another useful formula
P(A) = P(A|B) x P(B) + P(A|B') x P(B)
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Another useful formula
P(A u B) = P(A) + P(B) - P(A) x P(B)
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## Other cards in this set

### Card 2

#### Front

P(A n B) = P(A n B) / P(A) ∴ P(A|B) = P(A n B) / P(B)

#### Back

Conditional Probability

### Card 3

#### Front

P(A n B) = P(B|A) x P(A) OR P(A n B) = P(A|B) x P(B)

### Card 4

#### Front

P(A or B) = P(A) + P(B) -- P(A n B) = 0

### Card 5

#### Front

P(A n B) = P(A) x P(B) -> P(A|B) = P(A) = P(AnB) = P(A) P(B)