7th Grade · Statistics & Probability
Dependent Events
7.SP.C.8
Definition
Events where the outcome of the first event changes the probability of the second. Occurs when drawing without replacement. P(A and B) = P(A) × P(B given A happened first).
Examples
- Bag with 3 red, 2 blue marbles: P(red first) = 3/5, then P(red second) = 2/4 if red was drawn first.
- P(red first AND red second) = 3/5 × 2/4 = 3/10.
Key rule
Without replacement signals dependent events — removing one item changes the pool.
Memory hook
The first draw changes the odds for the second.