HW1
Date: 08/29/2009
MTHSC 805
Data Analysis
Fall 2009
Abhishek Pandey
1.
Problem 1.3
The objection made by participant is not valid because hardness of of items molded
from plastic
Y
does not only depends on natural chemical processes but there can
be other external factors also which affects it. For example,temperature in which
it is kept and it may not be possible to take into account of all the factors affecting
its hardness. So I think regression analysis is appropriate for the sitiuation.
2.
Problem 1.5
I do not agree with the student,since a simple regression model is given by
Y
i
=
β
0
+
β
1
Xi
+
i
where error term
i
is random with mean
E
i
= 0
So it should be
E
(
Y
i
) =
E
[
β
0
+
β
1
X
i
+
i
] =
β
0
+
β
1
X
i
+
E
[
i
] =
β
0
+
β
1
X
i
(1)
3.
Problem 1.13
(a) Data used were observational,since there was no control over the study.
(b) A positive relation between participants productivity level and amount of
time spent in class participation may not imply that productivity is direct
result of time spent in class participation. It may be possible that people who
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 Fall '09
 Dr.F.Vera
 Linear Regression, Regression Analysis, Yi, Errors and residuals in statistics, Xi Yi − Xi Yi

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