Chapter 13: Problem 9
Explain the meaning and concept of SSE. You may use a graph for illustration purposes.
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Chapter 13: Problem 9
Explain the meaning and concept of SSE. You may use a graph for illustration purposes.
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Explain the meaning of the words simple and linear as used in simple linear regression.
Explain the least squares method and least squares regression line. Why are they called by these names?
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. $$ \begin{array}{cc} \hline \text { Income } & \text { Charitable Contributions } \\ \hline 76 & 15 \\ 57 & 4 \\ 140 & 42 \\ 97 & 33 \\ 75 & 5 \\ 107 & 32 \\ 65 & 10 \\ 77 & 18 \\ 102 & 28 \\ 53 & 4 \\ \hline \end{array} $$ a. With income as an independent variable and charitable contributions as a dependent variable, compute \(\mathrm{SS}_{x}, \mathrm{SS}_{y y}\), and \(\mathrm{SS}_{x y}\) 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 information is obtained for a sample of 25 observations taken from a population. \(\mathrm{SS}_{x x}=274.600, \quad s_{e}=.932, \quad\) and \(\quad \hat{y}=280.56-3.77 x\) a. Make a \(95 \%\) confidence interval for \(B\). b. Using a significance level of \(.01\), test whether \(B\) is negative. c. Testing at the \(5 \%\) significance level, can you conclude that \(B\) is different from zero? d. Test if \(B\) is different from \(-5.20\). Use \(\alpha=.01\).
The following table gives the average weekly retail price of a gallon of regular gasoline in the eastern United States over a 9-week period from December 1, 2014, through January 26, 2015. Consider these 9 weeks as a random sample. $$ \begin{array}{l|rrrrrr} \hline \text { Date } & 12 / 1 / 14 & 12 / 8 / 14 & 12 / 15 / 14 & 12 / 22 / 14 & 12 / 29 / 14 & 1 / 5 / 15 \\ \hline \text { Price (\$) } & 2.861 & 2.776 & 2.667 & 2.535 & 2.445 & 2.378 \\\ \hline \text { Date } & 1 / 12 / 15 & 1 / 19 / 15 & 1 / 26 / 15 & & & \\ \hline \text { Price (\$) } & 2.293 & 2.204 & 2.174 & & & \\ \hline \end{array} $$ a. Assign a value of 0 to \(12 / 1 / 14,1\) to \(12 / 8 / 14,2\) to \(12 / 15 / 14\), and so on. Call this new variable Time. Make a new table with the variables Time and Price. b. With time as an independent variable and price as the dependent variable, compute \(S S_{x x}, S S_{y y}\), and \(S S_{x y}\) c. Construct a scatter diagram for these data. Does the scatter diagram exhibit a negative linear relationship between time and price? d. Find the least squares regression line \(\hat{y}=a+b x\). e. Give a brief interpretation of the values of \(a\) and \(b\) calculated in part \(\mathrm{d}\). f. Compute the correlation coefficient \(r .\) g. Predict the average price of a gallon of regular gasoline in the eastern United States for Time \(=26 .\) Comment on this prediction.
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