Probability Formulae

Probability Formulas

1. Probability Range for an event A

$= 0 = P(A) = 1$

2. Rule of Complementary Events

$= P(A^c) + P(A) = 1$

3. Rule of Addition for events A and B

$P(A or B) = P(A) + P(B) – P(A \cap B)$

4. Disjoint Events
Events A and B are disjoint

$<=> P(A\cap B) = 0$

5. Conditional Probability i-e probability of event A subject to event B

$P(\frac{A}{B}) = \frac{P(A\cap B)} { P(B)}$

6. Baye’s Formula is

$P(\frac{A}{B}) = P(\frac{B}{A})\times \frac{ P(A)}{ P(B)}$

7. Independent Events
Events A and B are independent if and only if

$P(A\cap B) = P(A) \times P(B)$

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