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Stat 252
Exam 1
Rein
Fall 2008
1)
Identify each statement about independent samples Ttests and CIs as True or False.
a.
The higher the confidence level, the higher the margin of error.
b.
The higher the sample sizes, the higher the margin of error.
c.
The higher the standard deviations, the higher the margin of error.
d.
If a Confidence Interval for
ߤ
ଵ
െߤ
ଶ
includes zero and if
ݔҧ
ଵ
is larger than
ݔҧ
ଶ
, a null hypothesis of equality would
be rejected in favor of an alternative hypothesis of inequality.
e.
If a Confidence Interval for
ߤ
ଵ
ଶ
includes zero and if
ݔҧ
ଵ
is larger than
ݔҧ
ଶ
, a null hypothesis of equality would
be rejected in favor of an alternative hypothesis that
ߤ
ଵ
is larger than
ߤ
ଶ
.
f.
If a Confidence Interval for the difference of means is 2.1±1.1, it should be interpreted in plain English as “We
are 95% sure that
ݔҧ
ଵ
െݔҧ
ଶ
is in the 1.0 to 3.2 range.”
g.
If a Confidence Interval for the difference of means is 2.1±1.1, doubling the sample size for each group would cut
the margin of error approximately in half.
1a
True
1b
False
1c
True
1d
False
1e
False
1f
False
1g
False
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View Full Document Stat 252
Exam 1
Rein
Fall 2008
2)
To study the possibility of the housing market crash starting as early as 2005, data on singlefamily homes in Oakland
that sold in both 2006 and 2005 were collected and summary statistics from Minitab are presented:
Descriptive Statistics: 2005 Price ($1000s), 2006 Price ($1000s), Difference
Variable
N
Mean
StDev
2005 Price ($1000s)
18
477.9
66.2
2006 Price ($1000s)
18
447.0
46.9
Difference
18
30.9
24.1
a.
Develop an appropriate 95% Confidence interval for the mean change in price in Oakland between 2005 and 2006
based on these data.
For paired data like these, the equation for a 95% Confidence Interval is
݀
ҧ
േݐ
ఈ/ଶ
௦
ඥ
.
For these
data, the CI would thus be
݀
ҧ
ఈ/ଶ
௦
ඥ
ൌ 30.9 േ 2.1098
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This note was uploaded on 10/28/2008 for the course STAT 252 taught by Professor Staff during the Spring '05 term at Cal Poly.
 Spring '05
 staff
 Statistics

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