Note 2: We can use the probability distribution to calculate probabilities for associated events.

examples: Let X = number of heads observed when flipping a fair coin.

• What’s the probability of getting at least 2 heads?

P(X ≥ 2) = P(X = 2) + P(X = 3) + P(X = 4)

= 6/16 + 4/16 + 1/16 = 11/16

• What’s the probability of getting less than 4 heads?

P(X < 4) =