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Business statistics Study Set 3
Exam 19: Multiple Regression
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Question 81
True/False
A multiple regression analysis that includes 25 data points and 4 independent variables produces SST = 400 and SSR = 300. The multiple standard error of estimate will be 5.
Question 82
Essay
An economist wanted to develop a multiple regression model to enable him to predict the annual family expenditure on clothes. After some consideration, he developed the multiple regression model:
y
=
β
0
+
β
1
x
1
+
β
2
x
2
+
β
3
x
3
+
ε
y = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + \varepsilon
y
=
β
0
+
β
1
x
1
+
β
2
x
2
+
β
3
x
3
+
ε
. Where: y = annual family clothes expenditure (in $1000s)
x
1
x _ { 1 }
x
1
= annual household income (in $1000s)
x
2
x _ { 2 }
x
2
= number of family members
X
3
X _ { 3 }
X
3
= number of children under 10 years of age The computer output is shown below. THE REGRESSION EQUATION IS
y
=
1.74
+
0.091
x
1
+
0.93
x
2
+
0.26
x
3
y=1.74+0.091 x_{1}+0.93 x_{2}+0.26 x_{3}
y
=
1.74
+
0.091
x
1
+
0.93
x
2
+
0.26
x
3
Predictor
Coef
StDev
T
Constant
1.74
0.630
2.762
x
1
0.091
0.025
3.640
x
2
0.93
0.290
3.207
x
3
0.26
0.180
1.444
\begin{array}{|c|ccc|}\hline \text { Predictor } & \text { Coef } & \text { StDev } & \text { T } \\\hline \text { Constant } & 1.74 & 0.630 & 2.762 \\x_{1} & 0.091 & 0.025 & 3.640 \\x_{2} & 0.93 & 0.290 & 3.207 \\x_{3} & 0.26 & 0.180 & 1.444 \\\hline\end{array}
Predictor
Constant
x
1
x
2
x
3
Coef
1.74
0.091
0.93
0.26
StDev
0.630
0.025
0.290
0.180
T
2.762
3.640
3.207
1.444
S
=
2.06
R
−
S
q
=
59.6
%
\mathrm { S } = 2.06 \quad \mathrm { R } - \mathrm { Sq } = 59.6 \%
S
=
2.06
R
−
Sq
=
59.6%
ANALYSIS OF VARIANCE
Source of Variation
d
f
S
S
M
S
F
Regression
3
288
96
22.647
Error
46
195
4.239
Total
49
483
\begin{array}{|l|cccc|}\hline \text { Source of Variation } & \mathrm{df} & \mathrm{SS} & \mathrm{MS} & \mathrm{F} \\\hline \text { Regression } & 3 & 288 & 96 & 22.647 \\\text { Error } & 46 & 195 & 4.239 & \\\hline \text { Total } & 49 & 483 & & \\\hline\end{array}
Source of Variation
Regression
Error
Total
df
3
46
49
SS
288
195
483
MS
96
4.239
F
22.647
Test at the 1% significance level to determine whether the number of family members and annual family clothes expenditure are linearly related.
Question 83
Essay
A statistics professor investigated some of the factors that affect an individual student's final grade in his or her course. He proposed the multiple regression model:
y
=
β
0
+
β
1
x
1
+
β
2
x
2
+
β
3
x
3
+
ε
y = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + \varepsilon
y
=
β
0
+
β
1
x
1
+
β
2
x
2
+
β
3
x
3
+
ε
. Where: y = final mark (out of 100).
x
1
x _ { 1 }
x
1
= number of lectures skipped.
x
2
x _ { 2 }
x
2
= number of late assignments.
X
3
X _ { 3 }
X
3
= mid-term test mark (out of 100). The professor recorded the data for 50 randomly selected students. The computer output is shown below. THE REGRESSION EQUATION IS
=
41.6
−
3.18
x
1
−
1.17
x
2
+
.
63
x
3
= 41.6 - 3.18 x _ { 1 } - 1.17 x _ { 2 } + .63 x _ { 3 }
=
41.6
−
3.18
x
1
−
1.17
x
2
+
.63
x
3
Predictor
Coef
StDev
T
Constant
41.6
17.8
2.337
x
1
−
3.18
1.66
−
1.916
x
2
−
1.17
1.13
−
1.035
x
3
0.63
0.13
4.846
\begin{array}{|c|ccc|}\hline \text { Predictor } & \text { Coef } & \text { StDev } & \text { T } \\\hline \text { Constant } & 41.6 & 17.8 & 2.337 \\x_{1} & -3.18 & 1.66 & -1.916 \\x_{2} & -1.17 & 1.13 & -1.035 \\x_{3} & 0.63 & 0.13 & 4.846 \\\hline\end{array}
Predictor
Constant
x
1
x
2
x
3
Coef
41.6
−
3.18
−
1.17
0.63
StDev
17.8
1.66
1.13
0.13
T
2.337
−
1.916
−
1.035
4.846
S
=
13.74
R
−
S
q
=
30.0
%
\mathrm { S } = 13.74 \quad \mathrm { R } - \mathrm { Sq } = 30.0 \%
S
=
13.74
R
−
Sq
=
30.0%
ANALYSIS OF VARIANCE
Source of Variation
df
S
S
M
S
F
Regression
3
3716
1238.667
6.558
Error
46
8688
188.870
Total
49
12404
\begin{array}{|l|cccc|}\hline \text { Source of Variation } & \text { df } & \mathrm{SS} & \mathrm{MS} & \mathrm{F} \\\hline \text { Regression } & 3 & 3716 & 1238.667 & 6.558 \\\text { Error } & 46 & 8688 & 188.870 & \\\hline \text { Total } & 49 & 12404 & & \\\hline\end{array}
Source of Variation
Regression
Error
Total
df
3
46
49
SS
3716
8688
12404
MS
1238.667
188.870
F
6.558
Do these data provide enough evidence to conclude at the 5% significance level that the model is useful in predicting the final mark?
Question 84
Essay
An economist wanted to develop a multiple regression model to enable him to predict the annual family expenditure on clothes. After some consideration, he developed the multiple regression model:
y
=
β
0
+
β
1
x
1
+
β
2
x
2
+
β
3
x
3
+
ε
y = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + \varepsilon
y
=
β
0
+
β
1
x
1
+
β
2
x
2
+
β
3
x
3
+
ε
. Where: y = annual family clothes expenditure (in $1000s)
x
1
x _ { 1 }
x
1
= annual household income (in $1000s)
x
2
x _ { 2 }
x
2
= number of family members
X
3
X _ { 3 }
X
3
= number of children under 10 years of age The computer output is shown below. THE REGRESSION EQUATION IS
y
=
y =
y
=
1.74
+
0.091
x
1
+
0.93
x
2
+
0.26
x
3
1.74 + 0.091 x _ { 1 } + 0.93 x _ { 2 } + 0.26 x _ { 3 }
1.74
+
0.091
x
1
+
0.93
x
2
+
0.26
x
3
Predictor
Coef
StDev
T
Constant
1.74
0.630
2.762
x
1
0.091
0.025
3.640
x
2
0.93
0.290
3.207
x
3
0.26
0.180
1.444
\begin{array} { | c | c c c | } \hline \text { Predictor } & \text { Coef } & \text { StDev } & \mathrm { T } \\\hline \text { Constant } & 1.74 & 0.630 & 2.762 \\x _ { 1 } & 0.091 & 0.025 & 3.640 \\x _ { 2 } & 0.93 & 0.290 & 3.207 \\x _ { 3 } & 0.26 & 0.180 & 1.444 \\\hline\end{array}
Predictor
Constant
x
1
x
2
x
3
Coef
1.74
0.091
0.93
0.26
StDev
0.630
0.025
0.290
0.180
T
2.762
3.640
3.207
1.444
S = 2.06 R-Sq = 59.6%.
ANALYSIS OF VARIANCE
Source of Variation
df
SS
MS
F
Regression
3
288
96
22.647
Error
46
195
4.239
Total
49
483
\begin{array}{l}\text { ANALYSIS OF VARIANCE }\\\begin{array} { | l | c c c c | } \hline \text { Source of Variation } & \text { df } & \text { SS } & \text { MS } & \text { F } \\\hline \text { Regression } & 3 & 288 & 96 & 22.647 \\\text { Error } & 46 & 195 & 4.239 & \\\hline \text { Total } & 49 & 483 & & \\\hline\end{array}\end{array}
ANALYSIS OF VARIANCE
Source of Variation
Regression
Error
Total
df
3
46
49
SS
288
195
483
MS
96
4.239
F
22.647
Test the overall model's validity at the 5% significance level.
Question 85
Essay
Consider the following statistics of a multiple regression model: n = 30 k = 4 SS
y
= 1500 SSE = 260. a. Determine the standard error of estimate. b. Determine the multiple coefficient of determination. c. Determine the F-statistic.
Question 86
Multiple Choice
In a regression model involving 60 observations, the following estimated regression model was obtained:
=
51.4
+
0.70
x
1
+
0.679
x
2
−
0.378
x
3
= 51.4 + 0.70 x _ { 1 } + 0.679 x _ { 2 } - 0.378 x _ { 3 }
=
51.4
+
0.70
x
1
+
0.679
x
2
−
0.378
x
3
For this model, total variation in y = SSY = 119,724 and SSR = 29,029.72. The value of MSE is:
Question 87
Multiple Choice
For the estimated multiple regression model
= 30 -4x
1
+ 5x
2
+3 x
3
, a one unit increase in x
3
, holding x
1
and x
2
constant, will result in which of the following changes in y?
Question 88
Multiple Choice
In testing the validity of a multiple regression model in which there are four independent variables, the null hypothesis is:
Question 89
Essay
An actuary wanted to develop a model to predict how long individuals will live. After consulting a number of physicians, she collected the age at death (y), the average number of hours of exercise per week (
x
1
x _ { 1 }
x
1
), the cholesterol level (
x
2
x _ { 2 }
x
2
), and the number of points by which the individual's blood pressure exceeded the recommended value (
X
3
X _ { 3 }
X
3
). A random sample of 40 individuals was selected. The computer output of the multiple regression model is shown below: THE REGRESSION EQUATION IS
y
=
y =
y
=
55.8
+
1.79
x
1
−
0.021
x
2
−
0.016
x
3
55.8 + 1.79 x _ { 1 } - 0.021 x _ { 2 } - 0.016 x _ { 3 }
55.8
+
1.79
x
1
−
0.021
x
2
−
0.016
x
3
Predictor
Coef
StDev
T
Constant
55.8
11.8
4.729
x
1
1.79
0.44
4.068
x
2
−
0.021
0.011
−
1.909
x
3
−
0.016
0.014
−
1.143
\begin{array} { | c | c c c | } \hline \text { Predictor } & \text { Coef } & \text { StDev } & \text { T } \\\hline \text { Constant } & 55.8 & 11.8 & 4.729 \\x _ { 1 } & 1.79 & 0.44 & 4.068 \\x _ { 2 } & - 0.021 & 0.011 & - 1.909 \\x _ { 3 } & - 0.016 & 0.014 & - 1.143 \\\hline\end{array}
Predictor
Constant
x
1
x
2
x
3
Coef
55.8
1.79
−
0.021
−
0.016
StDev
11.8
0.44
0.011
0.014
T
4.729
4.068
−
1.909
−
1.143
S = 9.47 R-Sq = 22.5%.
ANALYSIS OF VARIANCE
Source of Variation
df
SS
MS
F
Regression
3
936
312
3.477
Error
36
3230
89.722
Total
39
4166
\begin{array}{l}\text { ANALYSIS OF VARIANCE }\\\begin{array} { | l | c c c c | } \hline \text { Source of Variation } & \text { df } & \text { SS } & \text { MS } & \text { F } \\\hline \text { Regression } & 3 & 936 & 312 & 3.477 \\\text { Error } & 36 & 3230 & 89.722 & \\\hline \text { Total } & 39 & 4166 & & \\\hline\end{array}\end{array}
ANALYSIS OF VARIANCE
Source of Variation
Regression
Error
Total
df
3
36
39
SS
936
3230
4166
MS
312
89.722
F
3.477
What is the coefficient of determination? What does this statistic tell you?
Question 90
True/False
In multiple regression, the problem of multicollinearity affects the t-tests of the individual coefficients as well as the F-test in the analysis of variance for regression, since the F-test combines these t-tests into a single test.