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Probability and Statistics
3.2 Extra Practice – Basic Probability
Name__________________________
1) Which of the following values cannot be probabilities?
2) Data collected by volunteers showed that 89 New York City subway cars had
broken doors and 286 cars did not. If a car is randomly selected, what is the
approximate probability that it will have broken doors?
3) Among 400 randomly selected drivers in the 20-24 age bracket, 136 were in a
car accident during the last year. If a driver in that age bracket is randomly
selected, what is the approximate probability that he or she will be in a car
accident within the next year?
4) Blood groups are determined for a sample of people, and the results are
given in the accompanying table. If one person from this sample group is
randomly selected, find the probability that the person has group AB blood.
Blood Group
O
A
B
AB
Frequency
90
80
20
10
5) The stem-and-leaf plot summarizes the time (in hours) managers spend in
one day on paperwork. Use this sample to estimate the probability that a
randomly selected manager spends more than 2.0 hours per day on paperwork.
Key: 2 0 = 2.0 hours
Stem
0
1
2
3
4
Leaf
0000
0578
00113449
347
445
6) On a quick quiz consisting of 3 true-false questions, an unprepared student
must guess at each one. The guesses will be random.
a) List the different possible solutions.
b) What is the probability of answering the 3 questions correctly?
c) What is the probability of guessing incorrectly for all three questions?
d) What is the probability of passing…that is, guessing correctly on at
least two of the questions?
7) Both parents have the brown-blue pair of eye-color genes, and each parent
contributes on gene to a child. Assume that if the child has at least one brown
gene, that the color will dominate and the child’s eyes will be brown. (Actually,
the determination of eye color is somewhat more complex.)
a) List the different possible outcomes. Assume that these outcomes are
equally likely.
b) What is the probability that a child of these parents will have the blueblue pair of genes?
c) What is the probability that the child has brown eyes?