Question

1. . If a 6-sided die is rolled, what is the probablilty of getting a 1 or an even?

(a) Suppose that 1/4 of all pet owners have their pets bathed professionally. If 8

pet owners are selected at random, what is the probability exactly 3 have their pets bathed

professionally?

(b) If 8 pet owners are selcted, what is the mean and standard deviation of the

number of pet owners have their pets bathed professionally?

Answer 1

1) P(1 or an even) = P(rolling 1) + P(rolling an even number) - P(rolling 1 and an even number)

                             = 1/6 + 3/6 - 0

                             = 4/6

                             = 2/3

2) p = 1/4 = 0.25

n = 8

a) P(X = 3) = 8C3 * 0.25³ * (1 - 0.25)^8-3 = 0.2076

b) mean = n * p = 8 * 0.25 = 2

standard deviation = sqrt(n * p * (1 - p)) = sqrt(8 * 0.25 * 0.75) = 1.22