AP Statistics / Unit 2: Probability, Random Variables, and Probability Distributions
2.8 Introduction to Random Variables and Probability Distributions
Notes
A random variable assigns a number to each outcome. Its probability distribution lists values and probabilities, which sum to 1.
- Discrete: countable values. Continuous: intervals, with area as probability.
Practice
$X$ takes 0, 1, 2 with probabilities 0.3, 0.5 and $p$. Then $p=$
They must sum to 1.
For a continuous random variable, $P(X=3)=$
A single point has no area.
The number of heads in 4 coin flips is:
It's a count.
Ready for more? Take the Unit 2 test.