Answers to Quizzes in Simple Linear Regression Lecture
Stat 372 Fall 2009
20
15
y2
15
5
5
10
10
y1
20
1. The rst plot looks roughly linear; for the second, there might be some curvature.
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1
2
x
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x
2. We get the values for y by pl
Solutions to Practice Problems
Stat 372 Fall 2009
4
6
density of mean length for 4 parts
2
density of part lengths
0
dnorm(xpl, 7, 0.05)
8
1. (a) and (c)
6.6
6.8
7.0
7.2
7.4
(b) About 16%, by the 689599.7 rule.
(d) About 2.5%.
(e) About 5%
(f) About 97.
Homework #1 solution
Stat 372 Fall 2009
hits misses % hits
60
40
1. Samantha 40
Jennifer 72
28
72
Near
hits misses % hits
Samantha 10
0
100
Jennifer 70
10
87.5
Far
hits misses % hits
Samantha 30
60
33.3
Jennifer
2
18
10
Although Jennifer has a higher over
Solutions for Homework #2
Stat 372 Fall 2009
1. Experiments: sh oil study, burger study. Observational studies: nightmare study,
caeine study, dorm study, and alzheimers study.
Fish Oil: The response variable is whether or not the person suered death,
str
Homework #3 solutions
Stat 372 Fall 2009
1. (a)
0.6
0.8
1.0
needle lengths
Species S
0.0
0.2
0.4
Species N

5.237
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7
8
(b) Clearly, smaller needle lengths support the alternative hypothesis. The level of
signicance is the probability of rejecting H0 ,
Homework #4 solutions
Stat 372 Fall 2009
1. (a) It is an experiment, because the predictor variable (which design) is determined
by the researcher.
(b) The SSA is easy to compute, because we dont need the sample variances. Using
that y = 371.33, we get SS
Homework #5 solutions
Stat 372 Fall 2009
1. (a) The best t line is y = 2.963 + 0.060x. We estimate that rabbits given no growth
hormone weight 2.963 pounds at three months. For each addition mp of growth
hormone, we estimate that the weight of the baby ra
Homework #6 solutions
Stat 372 Fall 2009
1. (a) pvalue > 0.5, since the mean sales with the cartoon is lower than the mean sales
without the cartoon. (no calculations necessary!)
(b) It is reasonable to assume that the advertising variable explains some