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Statistics for Business
Exam 13: Additional Topics in Regression Analysis
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Question 81
Essay
THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A market researcher is interested in the average amount of money spent per year by college students on clothing.From 25 years of annual data,the following estimated regression was obtained through least squares: y
t
= 48.75 +
+
+
where the numbers in parentheses below the coefficients are the coefficient standard errors,and y = Expenditure per student,in dollars,on clothes x
1
= Disposable income per student,in dollars,after the payment of tuition,fees,and room and board. x
2
= Index of advertising,aimed at the student market,on clothes -Briefly discuss what is meant by the "dummy variable trap".
Question 82
Essay
THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: An economist is in the process of developing a model to predict the price of gold.She believes that the two most important variables are the price of a barrel of oil (x
1
)and the interest rate (x
2
).She proposes the model y = β
0
+ β
1
x
1
+ β
2
x
2
+ β
3
x
1
x
3
+ ε.A random sample of 20 daily observations was taken.The computer output is shown below. THE REGRESSION EQUATION IS y = 115.6 + 22.3x
1
+ 14.7x
2
- 1.36x
1
x
2
S = 20.9 R-Sq = 55.4% ANALYSIS OF VARIANCE
-Suppose that the true linear model for a process was Y = β
0
+ β
1
X
1
+ β
2
X
2
+ β
3
X
3
and you incorrectly estimated the model y = α + α
1
X
2
.Discuss the bias that results from using the second model.
Question 83
Multiple Choice
Kurt is trying to regress a model that studies market prices between similar products from different companies.During his study he realized that one of the independent variables,the competitor's price,was causing multicollinearity issues with the model.If Kurt removes the variable from the model,which of the following statistical phenomenon could affect Kurt's model?
Question 84
Essay
The model y
t
= 8 + 2.1x
t
+ 0.25y
t
-1
is estimated using regression analysis applied to time-series data.What is the effect of a 1-unit increase in x in period (t + 1)?
Question 85
Short Answer
Consider the following model: Y
t
= β
0
+ β
1
x
1
t
+ β
2
x
2
t
+ β
3
3
x
3
t
+ γ
4
Y
t
-1
.Suppose we increase X
1
by one unit in time period t with all other independent variables in the model held fixed.What is the total expected increase in the dependent variable over all current and future time periods?
Question 86
Multiple Choice
In a regression model such as y = β
0
+ β
1
X
1
+ β
2
X
2
+ ε,if changes in x
1
and x
2
happen simultaneously,the model is said to be affected by: