Chapter 14: Problem 27
What do the y-coordinates on the least-squares regression line represent?
Short Answer
Step by step solution
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none}
Learning Materials
Features
Discover
Chapter 14: Problem 27
What do the y-coordinates on the least-squares regression line represent?
These are the key concepts you need to understand to accurately answer the question.
All the tools & learning materials you need for study success - in one app.
Get started for free
You obtain the multiple regression equation \(\hat{y}=5+3 x_{1}-4 x_{2}\) from a set of sample data. (a) Interpret the slope coefficients for \(x_{1}\) and \(x_{2}\). (b) Determine the regression equation with \(x_{1}=10\). Graph the regression equation with \(x_{1}=10\). (c) Determine the regression equation with \(x_{1}=15 .\) Graph the regression equation with \(x_{1}=15\) (d) Determine the regression equation with \(x_{1}=20 .\) Graph the regression equation with \(x_{1}=20 .\) (e) What is the effect of changing the value \(x_{1}\) on the graph of the regression equation?
Researchers developed a model to explain the age gap between husbands and wives at first marriage. The model is below: $$ \hat{y}=0.0321 x_{1}+0.9848 x_{2}+0.5391 x_{3}-0.000145 x_{4}^{2}+3.8483 $$ where y: Age gap at first marriage (male - female) \(x_{1}:\) Percent of children aged 10 to 14 involved in child labor \(x_{2}:\) Indicator variable where 1 is an African country, 0 otherwise \(x_{3}:\) Percent of the population that is Muslim \(x_{4}:\) Percent of the population that is literate Source: Xu Zhang and Solomon W. Polachek, State University of New York at Binghamton "The Husband- Wife Age Gap at First Marriage: A Cross-Country Analysis" (a) Use the model to predict the age gap at first marriage for an African country where the percent of children aged 10 to 14 who are involved in child labor is \(12,\) the percent of the population that is Muslim is \(30,\) and the percent of the population that is literate is \(75 .\) (b) What would be the mean difference in age gap between an African country and a non-African country? (c) Interpret the coefficient of "percent of children aged 10 to 14 involved in child labor." (d) The coefficient of determination for this model is 0.593 . Interpret this result. (e) The \(P\) -value for the test \(H_{1}: \beta_{1} \neq 0\) versus \(H_{1}: \beta_{1} \neq 0\) is \(0.008 .\) What would you conclude about this test?
For the data set. $$ \begin{array}{cllc} x_{1} & x_{2} & x_{3} & y \\ \hline 0.8 & 2.8 & 2.5 & 11.0 \\ \hline 3.9 & 2.6 & 5.7 & 10.8 \\ \hline 1.8 & 2.4 & 7.8 & 10.6 \\\ \hline 5.1 & 2.3 & 7.1 & 10.3 \\ \hline 4.9 & 2.5 & 5.9 & 10.3 \\ \hline 8.4 & 2.1 & 8.6 & 10.3 \\ \hline 12.9 & 2.3 & 9.2 & 10.0 \\ \hline 6.0 & 2.0 & 1.2 & 9.4 \\ \hline 14.6 & 2.2 & 3.7 & 8.7 \\ \hline 93 & 11 & 55 & 87 \end{array} $$ (a) Construct a correlation matrix between \(x_{1}, x_{2}, x_{3},\) and \(y .\) Is there any evidence that multicollinearity exists? Why? (b) Determine the multiple regression line with \(x_{1}, x_{2},\) and \(x_{3}\) as the explanatory variables. (c) Assuming that the requirements of the model are satisfied, test \(H_{0}: \beta_{1}=\beta_{2}=\beta_{3}=0\) versus \(H_{1}:\) at least one of the \(\beta_{i}\) is different from zero at the \(\alpha=0.05\) level of significance. (d) Assuming that the requirements of the model are satisfied, test \(H_{0}: \beta_{i}=0\) versus \(H_{1}: \beta_{i} \neq 0\) for \(i=1,2,3\) at the \(\alpha=0.05\) level of significance.
4\. Suppose you want to develop a model that predicts the gas mileage of a car. The explanatory variables you are going to utilize are \(x_{1}:\) city or highway driving \(x_{2}:\) weight of the car \(x_{3}:\) tire pressure (a) Write a model that utilizes all three explanatory variables in an additive model with linear terms and define any indicator variables. (b) Suppose you suspect there is interaction between weight and tire pressure. Write a model that incorporates this interaction term into the model from part (a).
An economist was interested in modeling the relation among annual income, level of education, and work experience. The level of education is the number of years of education beyond eighth grade, so 1 represents completing I year of high school, 8 means completing 4 years of college, and so on. Work experience is the number of years employed in the current profession. From a random sample of 12 individuals, he obtained the following data: $$ \begin{array}{ccc} \begin{array}{l} \text { Work Experience } \\ \text { (years) } \end{array} & \begin{array}{l} \text { Level of } \\ \text { Education } \end{array} & \begin{array}{l} \text { Annual Income } \\ \text { (\$ thousands) } \end{array} \\ \hline 21 & 6 & 34.7 \\ \hline 14 & 3 & 17.9 \\ \hline 4 & 8 & 22.7 \\\ \hline 16 & 8 & 63.1 \\ \hline 12 & 4 & 33.0 \\ \hline 20 & 4 & 41.4 \\\ \hline 25 & 1 & 20.7 \\ \hline 8 & 3 & 14.6 \\ \hline 24 & 12 & 97.3 \\\ \hline 28 & 9 & 72.1 \\ \hline 4 & 11 & 49.1 \\ \hline 15 & 4 & 52.0 \\\ \hline \end{array} $$ (a) Construct a correlation matrix between work experience, level of education, and annual income. Is there any reason to be concerned with multicollinearity based on the correlation matrix? (b) Find the least-squares regression equation \(\hat{y}=b_{0}+\) \(b_{1} x_{1}+b_{2} x_{2},\) where \(x_{1}\) is work experience, \(x_{2}\) is level of education, and \(y\) is the response variable, annual income. (c) Draw residual plots and a boxplot of the residuals to assess the adequacy of the model. (d) Interpret the regression coefficients for the least-squares regression equation. (e) Determine and interpret \(R^{2}\) and the adjusted \(R^{2}\) (f) Test \(H_{0}: \beta_{1}=\beta_{2}=0\) versus \(H_{1} ;\) at least one of the \(\beta_{i} \neq 0\) at the \(\alpha=0.05\) level of significance. (g) Test the hypotheses \(H_{0}: \beta_{1}=0\) versus \(H_{1}: \beta_{1} \neq 0\) and \(H_{0}: \beta_{2}=0\) versus \(H_{1}: \beta_{2} \neq 0\) at the \(\alpha=0.05\) level of significance. (h) Predict the mean income of all individuals whose experience is 12 years and level of education is 4 (i) Predict the income of a single individual whose experience is 12 years and level of education is 4 (j) Construct \(95 \%\) confidence and prediction intervals for income when experience is 12 years and level of education is 4
What do you think about this solution?
We value your feedback to improve our textbook solutions.