Prob Stat Chapter 5 Practice

It is estimated that 20 percent of all drivers do not signal when changing lanes. In a random sample of four drivers, what is the probability that at least one doesn't signal when changing lanes?

• 1-(0.2)^4

• 1-(0.8)^4

• 4(0.2)(0.8)^3

• 4(0.2)^3(0.8)

• 4(0.2)^3(0.8)+6(0.2)^2(0.8)^2+4(0.2)(0.8)^3+(0.8)^4

Suppose that the probabilities that an answer can be found on Google is 0.95, on Answers.com is 0.92, and on both Web sites is 0.874. Are the possibilities of finding the answer on the two Web sites independent?

• Yes, because (0.95)(0.92)=0.874

• No, because (0.95)(0.92)=0.874

• Yes because 0.95>0.92>0.874

• No, because 0.5(0.95+0.92) =/= 0.874

• There is insufficient information to answer this question

Three-fourths of college students change their major at least once. The reasons for changing and what they change to are given in the table. Assuming reasons and what students change to are independent, what is the probability that a college student decides to change a major, based on advisor suggestion, to pre-professional?

• 0.0263

• 0.0350

• 0.0467

• 0.3000

• 0.4500

Given the probabilities P(A)=0.03 and P(A U B)=0.7, what is the probability P(B) if A and B are mutually exclusive? If A and B are independent?

• 0.4, 0.3

• 0.4, 4/7

• 4/7, 0.4

• 0.7, 4/7

• 0.7, 0.3

Suppose that for a certain coastal city, in any given year the probability of a major hurricane hitting is 0.5, the probability of flooding is 0.3, and the probability of both a major hurricane and flooding is 0.2. What is the probability of flooding given that a major hurricane hits?

• 0.200

• 0.286

• 0.400

• 0.667

• 0.750

Suppose P(X) = 0.25 and P(Y)=0.40. If P(X given Y)=0.2, what is P(Y given X)?

• 0.10

• 0.125

• 0.32

• 0.45

• 0.50

Suppose that 62 percent of the graduates from your high school go on to four-year colleges, 15 percent go on to two-year colleges, 18 percent find employment, and the remaining graduates search for a job. If a randomly selected student is not going on to a four-year college, what is the probability he or she will find employment?

• 0.440

• 0.474

• 0.526

• 0.545

• 0.560

Suppose two events, E and F, have nonzero probabilities p and q, respectively. Which of the following is impossible?

• p+q>1

• p-q<0

• p/q=1

• E and F are neither independent nor mutually exclusive

• E and F are both independent and mutually exclusive