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Analysis of Variance
Reserve Supplemental Exercises Chapter 12 Problem 5
The data shown in the table below represent the thrust of a jet-turbine engine (y) and six
candidate regressors:
= primary speed of rotation,
= secondary speed of rotation,
= fuel
flow rate,
= pressure,
= exhaust temperature, and
= ambient temperature at time of test.
Fit the model using
as the response variable and
as the regressor (along with
and
).
Liquid soap
-0.00268
-0.05
0.966
Sugar
3.232
1.04
0.408
Glycerol
0.2357
-1.12
0.379
Water
0.1520
-1.66
0.239
S = 0.0323160 R-Sq = 71.9% R-Sq(adj) = 15.7%
(a) Test for significance of regression using
. Find the P-value for this test and state your
conclusions.
(b) Use the t-statistic to test
:
versus
:
for each variable in the model. If
, what conclusions can you draw?
SOLUTION
(a)
10.30
184.00
1662.00
8.32
10.29
164.00
1598.00
8.20
10.27
144.00
1541.00
8.07
10.31
216.00
1709.00
8.48
10.30
206.00
1669.00
8.44
10.30
196.00
1640.00
8.38
10.28
171.00
1572.00
8.25
10.31
184.00
1714.00
8.34
10.30
173.00
1679.00
8.29
10.29
153.00
1621.00
8.17
10.27
133.00
1561.00
8.03
10.31
198.00
1729.00
8.38
10.31
186.00
1692.00
8.33
10.30
178.00
1667.00
8.28
10.29
156.00
1609.00
8.15
10.27
136.00
1552.00
8.03
10.31
197.00
1758.00
8.39
10.31
188.00
1729.00
8.34
10.30
178.00
1690.00
8.29
10.29
156.00
1616.00
8.17
( )
1
0
1
1.3tse
= = −
10.31527
193
1748
8.373323
Reserve Supplemental Exercises Chapter 12 Problem 6
The data shown in the table below represent the thrust of a jet-turbine engine (y) and six
candidate regressors:
= primary speed of rotation,
= secondary speed of rotation,
= fuel
flow rate,
= pressure,
= exhaust temperature, and
= ambient temperature at time of test.
Fit the model using
as the response variable and
as the regressor (along with
and
).
(a) Use all possible regressions to select the best regression equation, where the model with the
minimum value of MSE is to be selected as “best”.
(b) Repeat part (a) using the minimum
criterion to identify the best equation.
(c) Use stepwise regression to select a subset regression model.
(d) Compare the models obtained in parts (a), (b), and (c).
(e) Consider the three-variable regression model. Calculate the variance inflation factors for this
model.
Would you conclude that multicollinearity is a problem in this model?
SOLUTION
(a)
10.31
195.00
1697.00
8.37
10.29
164.00
1598.00
8.20
Following minimum MSE criterion one should use all three regressors:
(b) Following minimum CP criterion one should use regressors
and
:
Reserve Supplemental Exercises Chapter 12 Problem 7
Tables given below present statistics for the Major League Baseball season.
10.31
197.00
1758.00
8.39
Major League Baseball Season
Major League Baseball 2005
Grounded into double play
(a) Consider the batting data. Use model-building methods to predict wins from the other
variables. Use Cp criterion.
(b) Repeat part (a) for the pitching data.
(c) Use both the batting and pitching data to build a model to predict wins.
SOLUTION
(a) Minimum Cp is –1.3 with the regressors HRb, BBb, SOb, and SBb (the subscript “b” denotes