AP Statistics - Chapter 4A Extra Practice
4. If the individual outcomes of a phenomenon are uncertain, but there is nonetheless a regular distribution of
outcomes in a large number of repetitions, we say the phenomenon is
A) random
B) predictable
C) deterministic
D) none of the above
5. I toss a thumb tack 60 times and it lands point up on 35 of the tosses. The experimental probability of landing point
up is
A) 35
B) 0.35
C) 0.58
D) 0.65
8. In a particular game, a fair die is tossed. If the number of spots showing is either 4 or 5 you win $1; if number of
spots showing is 6 you win $4; and if the number of spots showing is 1, 2, or 3 you win nothing. If it costs you $1
to play the game, the probability that you win more than the cost of playing is
A) 0
B) 1/6
C) 1/3
D) 2/3
10. A game consists of drawing three cards at random from a deck of playing cards. You win $3 for each red card that
is drawn. It costs $2 to play. For one play of this game, the sample space S for the net amount you win (after
deducting the cost of play) is
A) S = {$0, $1, $2, $3}
B) S = {$0, $3, $6, $9}
C) S = { –$2, $1, $4, $7}
D) S = { –$2, $3, $6, $9}
15. Event A occurs with probability 0.3. If event A and B are disjoint then
A) P(B)  0.3
B) P(B)  0.3
C) P(B)  0.7
D) P(B)  0.7
16. Students at University X must be in one of the class ranks—freshman, sophomore, junior, or senior. At University
X, 35% of the students are freshmen and 30% are sophomores. If a student is selected at random, the probability
that her or she is either a junior or a senior is
A) 30%
B) 35%
C) 65%
D) 70%
18. I flip a coin twice and count the number of heads, which of the following is a valid probability model for the
number of heads observed in two flips?
A) Number of Heads
0
1
2
Probability
1/3
1/3
1/3
B) Number of Heads
0
1
2
Probability
1/4
1/4
1/4
C) Number of Heads
0
1
2
Probability
1/3
1/2
1/3
D) None of the above.
Ignoring twins and other multiple births, assume babies born at a hospital are independent events with the probability that a
baby is a boy and the probability that a baby is a girl both equal to 0.5.
22. Referring to the information above, the probability that the next three babies are of the same sex is
A) 1.0
B) 0.125
C) 0.250
D) 0.500
23. Referring to the information above, the probability that at least one of the next three babies is a boy is
A) 0.125
B) 0.333
C) 0.75
D) 0.875
24. Referring to the information above, the events
A = the next two babies are boys
B = at least one of the next two babies is a boy
A) disjoint
B) complements
C) independent
D) none of the above
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are
27. In a certain town 60% of the households own a cellular phone, 40% own a pager, and 20% own both a cellular
phone and a pager. The proportion of households that own a cellular phone but not a pager is
A) 20%
B) 30%
C) 40%
D) 50%
34. Event A occurs with probability 0.4. The conditional probability that A occurs given that B occurs is 0.5, while the
conditional probability that A occurs given that B does not occur is 0.2. What is the conditional probability that B
occurs given that A occurs?
A) 0
B) 4/7
C) 5/8
D) this cannot be determined from the information given
35. Event A occurs with probability 0.8. The conditional probability that event B occurs given that A occurs is 0.5.
The probability that both A and B occur
A) is 0.3
B) is 0.4
C) is 0.8
D) cannot be determined from the information given
36. Event A occurs with probability 0.3 and event B occurs with probability 0.4. If A and B are independent, we may
conclude
A) P(A and B) = 0.12
B) P(A|B) = 0.3
C) P(B|A) = 0.4
D) all of the above
37. A plumbing contractor puts in bids in on two large jobs. Let the event that the contractor wins the first contract be
A and the event that the contractor wins the second contract be B. Which of the Venn diagrams on this page has
shaded the event that the contractor wins exactly one of the contracts?
A)
B)
C)
D)
38. The probability of a randomly selected adult having a rare disease for which a diagnostic test has been developed is
0.001. The diagnostic test is not perfect. The probability the test will be positive (indicating that the person has the
disease) is 0.99 for a person with the disease and 0.02 for a person without the disease. The proportion of adults for
which the test would be positive is
A) 0.00099
B) 0.01998
C) 0.02097
D) 0.02100
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