Exam 17: Multiple Regression

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A high value of the coefficient of determination significantly above 0 in multiple regression,accompanied by insignificant t-statistics on all parameter estimates,very often indicates a high correlation between independent variables in the model.

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In calculating the standard error of the estimate, sz=MSEs _ { z } = \sqrt { \mathrm { MSE } } ,there are (n \le k \le 1)degrees of freedom,where n is the sample size and k is the number of independent variables in the model.

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In a multiple regression model,the following statistics are given: SSE = 100,R2 = 0.995,k = 5,and n = 15.Then,the coefficient of determination adjusted for degrees of freedom is:

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One of the consequences of multicollinearity in multiple regression is biased estimates on the slope coefficients.

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Multicollinearity is present if the dependent variable is linearly related to one of the explanatory variables.

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Multicollinearity affects the t-tests of the individual coefficients as well as the F-test in the analysis of variance for regression because the F-test combines the t-tests into a single test.

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A(n)____________________ value of the F-test statistic indicates that the multiple regression model is valid.

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The total variation in y is equal to SSR + ____________________.

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If multicollinearity exists among the independent variables included in a multiple regression model,then:

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Multicollinearity will result in excessively low standard errors of the parameter estimates reported in the regression output.

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In a multiple regression model,the probability distribution of the error variable ε\varepsilon is assumed to be:

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The Durbin-Watson d statistic is used to check the assumption of normality.

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When an explanatory variable is dropped from a multiple regression model,the coefficient of determination can increase.

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In a multiple regression analysis involving 6 independent variables,the total variation in y is 900 and SSR = 600.What is the value of SSE?

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In a multiple regression analysis,there are 20 data points and 4 independent variables,and the sum of the squared differences between observed and predicted values of y is 180.The standard error of estimate will be:

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Which of the following statements regarding multicollinearity is not true?

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The parameter estimates are biased when multicollinearity is present in a multiple regression equation.

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A multiple regression model has the form y~=b0+b1x1+b2x2\tilde { y } = b _ { 0 } + b _ { 1 } x _ { 1 } + b _ { 2 } x _ { 2 } .The coefficient b1 is interpreted as the change in the average value of y per unit change in ________ holding ________ constant.

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Real Estate Builder A real estate builder wishes to determine how house size is influenced by family income,family size,and education of the head of household.House size is measured in hundreds of square feet,income is measured in thousands of dollars,and education is measured in years.A partial computer output is shown below. SUMMARY OUTPUT Regression Statistics Multiple R 0.865 R Square 0.748 Adjusted R Square 0.726 Standard Error 5.195 Observations 50 ANOVA  Real Estate Builder A real estate builder wishes to determine how house size is influenced by family income,family size,and education of the head of household.House size is measured in hundreds of square feet,income is measured in thousands of dollars,and education is measured in years.A partial computer output is shown below. SUMMARY OUTPUT   \begin{array}{l} \text { Regression Statistics }\\ \begin{array} { l l }  \text { Multiple R } & 0.865 \\ \text { R Square } & 0.748 \\ \text { Adjusted R Square } & 0.726 \\ \text { Standard Error } & 5.195 \\ \text { Observations } & 50 \end{array} \end{array}  ANOVA     \begin{array} { | l | c c c c | }  \hline & \text { Coeff } & \text { St. Error } & \boldsymbol { t }\boldsymbol {Sat } & \boldsymbol { P } \text {-value } \\ \hline \text { Intercept } & - 1.6335 & 5.807 \mathrm { 8 } & - 0.281 & 0 .7798 \\ \text { Family Incame } & 0.4485 & 0.1137 & 3.9545 & 0 .0003 \\ \text { Family Size } & 4.2615 & 0.8062 & 5.286 & 0 .0001 \\ \text { Education } & - 0.6517 & 0.4319 & - 1.509 & 0 .1383 \\ \hline \end{array}  -{Real Estate Builder Narrative} One individual in the sample had an annual income of $10,000,a family size of 1,and an education of 8 years.This individual owned a home with an area of 1,000 square fee (House = 10.00).What is the residual (in hundreds of square feet)for this data point? Coeff St. Error -value Intercept -1.6335 5.807 -0.281 0.7798 Family Incame 0.4485 0.1137 3.9545 0.0003 Family Size 4.2615 0.8062 5.286 0.0001 Education -0.6517 0.4319 -1.509 0.1383 -{Real Estate Builder Narrative} One individual in the sample had an annual income of $10,000,a family size of 1,and an education of 8 years.This individual owned a home with an area of 1,000 square fee (House = 10.00).What is the residual (in hundreds of square feet)for this data point?

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Student's Final Grade A statistics professor investigated some of the factors that affect an individual student's final grade in her course.She proposed the multiple regression model y=β0+β1x1+β2x2+β3x3+y = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + € ,where y is the final grade (out of 100 points),x1 is the number of lectures skipped,x2 is the number of late assignments,and x3 is the midterm exam score (out of 100).The professor recorded the data for 50 randomly selected students.The computer output is shown below. THE REGRESSION EQUATION IS y~=41.63.18x11.17x2+.63x3\tilde { y } = 41.6 - 3.18 x _ { 1 } - 1.17 x _ { 2 } + .63 x _ { 3 } Predicter Coef StDsv T Constant 41.6 17.8 2.337 -3.18 1.66 -1.916 -1.17 1.13 -1.035 0.63 0.13 4.846 S=13.74RSq=30.0%S = 13.74 \quad R - S q = 30.0 \% ANALYSIS OF VARIANCE Source of Variation Repressian 3 3716 1238.667 6.558 Esrar 46 8688 188.870 Total 49 12404 -{Student's Final Grade Narrative} What is the coefficient of determination? What does this statistic tell you?

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