Final exam
May 26, 2005
Directions
1.
There are 6 pages in this examination paper (including this). Check to make
sure you have a complete set and notify the invigilator immediately if part of it
is missing.
2.
Key formulas and statistical tables (
z
and
t
) are provided separately.
3.
Calculator may be used in this examination.
4.
You are given 3 hours to complete this examination. Do not begin until you
are told to do so.
1
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View Full DocumentAnswer the following questions, please provide steps that supports you answers
1. (15pts) A large public utility company wants to compare the consumption of electricity during the
summer season for singlefamily houses in two counties that it serves. For each household sampled,
the monthly electric bill is recorded with the following results:
County I
County II
n
25
25
X
$115
$98
s
$30
$25
Let
1
be the mean utility bill in county I and
2
be the mean utility bill in county II.
(b) What assumption was made in (a)?
(c) Find the pvalue in the testing in (a)
(d) Is there evidence that the mean monthly bill is higher in county I than in county II at 0.05 level
(e) What assumption was made in (b)?
county I and county II.
2. (12pts) The
New York Times
reported a study conducted by researchers concerning the role of media
in the lives of children. In one question of the study, children were asked if they use a computer each
day.
From a sample of 1090 children between the ages of 2 and 7, 283 used a computer each day.
From a sample of 2065 children between the ages of 8 and 18, 1053 used a computer each day. Let
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 Spring '09
 AnthonyChan
 Statistics, Econometrics, Linear Regression, Regression Analysis, Errors and residuals in statistics, mobile phone users

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