Binomial Distribution
1. A random variable X has a binomial distribution with mean
6 and variance 3.6. Find P(X = 4).
2. A certain type of mint has a label weight of 20.4 grams.
Suppose that the probability is 0.90 that a mint weighs more than 20.7 grams.
Let X equal the number of mints that weigh more than 20.7 grams in a sample of
eight mints selected at random.
a) How is X distributed if we assume independence?
b) Find:
(i) P(X = 8)
(ii) P(X ? 6)
(iii) P(X ? 6)
3. Suppose that the percentage of American drivers who are
multitaskers (e.g., talk on cell phones, eat a snack, or text message at the
same time they are driving) is approximately 80%. In a random sample of n = 20
drivers, let X equal the number of multitaskers.
a) How is X distributed?
b) Give the values of the mean, variance, and standard
deviation of X.
c) Find:
(i) P(X = 15)
(ii) P(X > 15)
(iii) P(X ? 15)





