1
CHAPTER 12 SECTION 1: INFERENCE ABOUT A POPULATION
MULTIPLE CHOICE
1.
Researchers determined that 60 Kleenex tissues is the average number of tissues used during a cold.
Suppose a random sample of 100 Kleenex users yielded the following data on the number of tissues
used during a cold:
x
= 52 and
s
= 22. Suppose the test statistic does not fall in the rejection region at
α
= 0.05. Which of the following conclusions is correct?
a.
At
= 0.05, we do not reject
H
0
.
b.
At
= 0.05, we reject
H
0
.
c.
At
= 0.05, we accept
H
0
.
d.
Both a and c.
ANS: A
PTS:
1
REF:
SECTION 12.1
2.
A robust estimator is one that is:
a.
unbiased and symmetrical about zero.
b.
consistent and is also moundshaped.
c.
efficient and less spread out.
d.
not sensitive to moderate nonnormality.
ANS: D
PTS:
1
REF:
SECTION 12.1
3.
For statistical inference about the mean of a single population when the population standard deviation is
unknown, the degrees for freedom for the
t
distribution equal
n

1 because we lose one degree of
freedom by using the:
a.
sample mean as an estimate of the population mean.
b.
sample standard deviation as an estimate of the population standard deviation.
c.
sample proportion as an estimate of the population proportion.
d.
sample size as an estimate of the population size.
ANS: A
PTS:
1
REF:
SECTION 12.1
4.
Researchers determined that 60 Kleenex tissues is the average number of tissues used during a cold.
Suppose a random sample of 100 Kleenex users yielded the following data on the number of tissues
used during a cold:
x
= 52 and
s
= 22. Suppose the alternative we wanted to test was
H
1
:
μ
< 60. The
correct rejection region for
= 0.05 is:
a.
reject
H
0
if
t
> 1.6604.
b.
reject
H
0
if
t
<

1.6604.
c.
reject
H
0
if
t
> 1.9842 or
Z
<

1.9842.
d.
reject
H
0
if
t
<

1.9842.
ANS: B
PTS:
1
REF:
SECTION 12.1
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5.
A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75
and a sample variance of 25. The upper limit of a 95% confidence interval for the population mean
would equal:
a.
77.77
b.
72.23
c.
88.85
d.
77.27
ANS: A
PTS:
1
REF:
SECTION 12.1
6.
A major department store chain is interested in estimating the average amount its credit card customers
spent on their first visit to the chain's new store in the mall. Fifteen credit card accounts were randomly
sampled and analyzed with the following results:
x
= $50.50 and
s
2
= 400. A 95% confidence interval
for the average amount the credit card customers spent on their first visit to the chain's new store in the
mall is:
a.
$50.50
±
$9.09.
b.
$50.50
±
$10.12.
c.
$50.50
±
$11.08.
d.
None of these choices.
ANS: C
PTS:
1
REF:
SECTION 12.1
7.
Researchers determine that 60 Kleenex tissues is the average number of tissues used during a cold.
Suppose a random sample of 100 Kleenex users yielded the following data on the number of tissues
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 Spring '10
 Kumar
 Statistics, Normal Distribution, Standard Deviation, Statistical hypothesis testing

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