Download Name: Date: ______ Section: 7.6 Similar to Exercise: 7.6.5a ___ 1

Unit 7 Review #2
Name: __________________________ Date: _____________
Section: 7.6
Similar to Exercise: 7.6.5a
___ 1. Suppose that more than a decade ago high levels of lead in the blood put 72% of children at risk. A
concerted effort was made to remove lead from the environment. Suppose, according to a survey,
only 9% of children in the United States are at risk of high blood-lead levels. In a random sample of
250 children taken more than a decade ago, what is the probability that 160 or more had high bloodlead levels?
A) 0.602 B) 0.858 C) 1.000 D) 0.000 E) 0.580
Ans: C
Section: 7.1
Similar to Exercise: 7.1.4e
___ 2. True or false: Consider two normal curves. If the first one has a larger mean than the second one,
then it also has a larger standard deviation than the second one.
A) false B) true
Ans: A
Section: 7.6
Similar to Exercise: 7.6.10c
___ 3. Suppose that about 66% of the people who are murdered actually knew the person who committed
the murder. Suppose that a detective file in Boston has 66 current unsolved murders. What is the
probability that fewer than 22 victims did not know their murderer?
A) 0.454 B) 0.506 C) 0.494 D) 0.596 E) 0.404
Ans: E
Section: 7.2
Similar to Exercise: 7.2.9a
___ 4. Let x = red blood cell (RBC) count in millions per cubic millimeter of whole blood. Suppose for
healthy females, x has an approximately normal distribution with mean μ = 4.2 and standard
deviation σ = 0.6. Convert the following x interval from a laboratory test to a z interval.
A) 2 > z
Ans: C
B) –4 > z
C) 2 < z
5.4 < x
D) 3 > z E) 0 < z
Section: 7.5
Similar to Exercise: 7.5.6a
___ 5. Suppose x has a distribution with μ = 81 and σ = 9. If random samples of size n = 26 are selected,
can we say that the distribution of sample means x for samples of this size is approximately
normal?
A) yes B) no
Ans: B
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Unit 7 Review #2
Section: 7.4
Similar to Exercise: 7.4.2
___ 6. What is a random sample of size n from a population?
A)
A random sample of size n from a population is a subset of the population selected in a
manner such that every sample of size n which contains the smallest or largest member of the
population.
B)
A random sample of size n from a population is a subset of the population of size n which
contains the mean of the population.
C)
A simple random sample of size n from a population is a subset of the population selected in a
manner such that every sample of size n from the population has an equal chance of being
selected and every member of the population has an equal chance of being included in the
sample.
D)
A random sample of size n from a population is a set of the population selected in a manner
such that every sample of size n containing the median has an equal chance of being selected.
E)
none of these choices
Ans: C
Section: 7.5
Similar to Exercise: 7.5.12ai
___ 7. The heights of 18-year-old men are approximately normally distributed with mean 68 inches and
standard deviation 3 inches. What is the probability that an 18-year-old man selected at random is
greater than 70 inches tall?
A) 0.7486 B) 0.2514 C) 0.2486 D) 0.4972 E) 0.5028
Ans: B
Section: 7.2
Similar to Exercise: 7.2.6
___ 8. Raul received a score of 71 on a history test for which the class mean was 61 with standard deviation
10. He received a score of 84 on a biology test for which the class mean was 79 with standard
deviation 2.5. On which test did he do better relative to the rest of the class?
A) history B) biology
Ans: B
Section: 7.1
Similar to Exercise: 7.1.2b
___ 9. Look at the normal curve given below, and find σ .
A) σ = 25
Ans: E
B) σ = 37
C) σ = 33
D) σ = 3
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E) σ = 4
Unit 7 Review #2
Section: 7.3
Similar to Exercise: 7.3.5
___ 10. Assume that x has a normal distribution, with the specified mean and standard deviation. Find the
indicated probabilities.
P (14 ≤ x ≤ 27 ) ; μ = 19; σ = 5
A) 0.726 B) 0.055 C) 0.945 D) 0.787 E) 0.841
Ans: D
Section: 7.2
Similar to Exercise: 7.2.8d
___ 11. Suppose a certain species of fawns between 1 and 5 months old have a body weight that is
approximately normally distributed with mean μ = 25.6 kilograms and standard deviation σ = 5
kilograms. Let x be the weight of a fawn in kilograms. Convert the following z interval to a x
interval.
A) x < –44.10
Ans: C
B) x > –44.10
–3.7 > z
C) x < 7.10 D) x > 44.10
E) x < –7.10
Section: 7.5
Similar to Exercise: 7.5.12bii
___ 12. The heights of 18-year-old men are approximately normally distributed with mean 68 inches and
standard deviation 3 inches. What is the probability that the average height x of a sample of ten 18year-old men will be between 67 and 68 inches?
A) 0.3531 B) 0.6469 C) 0.1469 D) 0.7062 E) 0.3661
Ans: A
Section: 7.3
Similar to Exercise: 7.3.29b
___ 13. A certain company makes 12-volt car batteries. After many years of product testing, the company
knows that the average life of a battery is normally distributed, with a mean of 40 months and a
standard deviation of 6 months. If the company does not want to make refunds for more than 10% of
its batteries under the full-refund guarantee policy, for how long should the company guarantee the
batteries (to the nearest month)?
A) 47 months B) 43 months C) 32 months D) 40 months E) 28 months
Ans: C
Section: 7.5
Similar to Exercise: 7.5.1
___ 14. True or false: The standard error of a sampling distribution is the difference between the mean and
the standard deviation.
A) true B) false
Ans: B
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Unit 7 Review #2
Section: 7.2
Similar to Exercise: 7.2.35
___ 15. Let z be a random variable with a standard normal distribution. Find the indicated probability below.
P ( z ≥ –1)
A) 0.841 B) 0.341 C) 0.921 D) 0.171 E) 0.079
Ans: A
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