7.1 Discrete Random Variables

3 practice questionsNot yet reviewed

Notes

A random variable assigns a number to each outcome of a random process. A discrete random variable has a countable list of possible values.

Its probability distribution lists each value with its probability.
Every probability is between 0 and 1, and the probabilities add to exactly 1.
Example: Let $X$ be the number of heads in two coin flips: $P(0) = 0.25$, $P(1) = 0.5$, $P(2) = 0.25$.

A random variable $X$ has $P(0) = 0.1$, $P(1) = 0.3$, $P(2) = p$ and $P(3) = 0.2$. What is $p$?

For the distribution $P(0) = 0.1$, $P(1) = 0.3$, $P(2) = 0.4$, $P(3) = 0.2$, what is $P(X \ge 2)$?

Which could be a probability distribution for $X = 1, 2, 3$?