Chapter 13: Problem 2
Explain the meaning of independent and dependent variables for a regression model.
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Chapter 13: Problem 2
Explain the meaning of independent and dependent variables for a regression model.
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The following table gives information on the incomes (in thousands of dollars) and charitable contributions (in hundreds of dollars) for the last year for a random sample of 10 households. $$ \begin{array}{rc} \hline \text { Income } & \text { Charitable Contributions } \\ \hline 76 & 15 \\ 57 & 4 \\ 140 & 42 \\ 97 & 33 \\ 75 & 5 \\ 107 & 32 \\ 65 & 10 \\ 77 & 18 \\ 102 & 28 \\ 53 & 4 \\ \hline \end{array} $$ a. With income as an independent variable and charitable contributions as a dependent variable, compute \(\mathrm{SS}_{x x}, \mathrm{SS}_{y y}\), and \(\mathrm{SS}_{x y^{\circ}}\) b. Find the regression of charitable contributions on income. c. Briefly explain the meaning of the values of \(a\) and \(b\). d. Calculate \(r\) and \(r^{2}\) and briefly explain what they mean. e. Compute the standard deviation of errors. f. Construct a \(99 \%\) confidence interval for \(B\). g. Test at a \(1 \%\) significance level whether \(B\) is positive. h. Using a \(1 \%\) significance level, can you conclude that the linear correlation coefficient is different from zero?
The following data give the ages (in years) of husbands and wives for six couples. $$ \begin{array}{l|cccccc} \hline \text { Husband's age } & 43 & 57 & 28 & 19 & 35 & 39 \\ \hline \text { Wife's age } & 37 & 51 & 32 & 20 & 33 & 38 \\ \hline \end{array} $$ a. Do you expect the ages of husbands and wives to be positively or negatively related? b. Plot a scatter diagram. By looking at the scatter diagram, do you expect the correlation coefficient between these two variables to be close to zero, 1, or \(-1 ?\) c. Find the correlation coefficient. Is the value of \(r\) consistent with what you expected in parts a and b? d. Using a \(5 \%\) significance level, test whether the correlation coefficient is different from zero.
Briefly explain the assumptions of the population regression model.
The following data give the experience (in years) and monthly salaries (in hundreds of dollars) of nine randomly selected secretaries. $$ \begin{array}{l|rrrrrrrrr} \hline \text { Experience } & 14 & 3 & 5 & 6 & 4 & 9 & 18 & 5 & 16 \\ \hline \text { Monthly salary } & 62 & 29 & 37 & 43 & 35 & 60 & 67 & 32 & 60 \\\ \hline \end{array} $$ a. Find the least squares regression line with experience as an independent variable and monthly salary as a dependent variable. b. Construct a \(98 \%\) confidence interval for \(B\). c. Test at the \(2.5 \%\) significance level whether \(B\) is greater than zero.
For a sample data set, the linear correlation coefficient \(r\) has a positive value. Which of the following is true about the slope \(b\) of the regression line estimated for the same sample data? a. The value of \(b\) will be positive. b. The value of \(b\) will be negative. c. The value of \(b\) can be positive or negative.
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