7th Grade · Statistics & Probability
Independent Events
7.SP.C.8
Definition
Two events where the outcome of one does not affect the probability of the other. P(A and B) = P(A) × P(B). Rolling dice and flipping coins are always independent.
Examples
- Flip a coin twice: P(Heads AND Heads) = 1/2 × 1/2 = 1/4.
- Roll a red die and a blue die: P(red=3 AND blue=5) = 1/6 × 1/6 = 1/36.
Key rule
Test for independence: is P(A AND B) = P(A) × P(B)? With replacement means independent.
Memory hook
One event doesn't change the other's odds.