Exam 17: Multiple Regression

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The range of the values of the Durbin-Watson statistic,d,is 0 \le d \le 4.

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Life Expectancy An actuary wanted to develop a model to predict how long individuals will live.After consulting a number of physicians,she collected the age at death (y),the average number of hours of exercise per week (x1),the cholesterol level (x2),and the number of points that the individual's blood pressure exceeded the recommended value (x3).A random sample of 40 individuals was selected.The computer output of the multiple regression model is shown below. THE REGRESSION EQUATION IS y = 55.8 + 1.79x1 -0.021x2 -0.061x3 Predicter Coef StDev T Constant 55.8 11.8 4.729 1.79 0.44 4.068 -0.021 0.011 -1.909 -0.016 0.014 -1.143 S=9.47RSq=22.5%S = 9.47 \quad R - S q = 22.5 \% ANALYSIS OF VARIANCE Source of Variation Repressian 3 936 312 3.477 Error 36 3230 89.722 Total 39 4166 -{Life Expectancy Narrative} Interpret the coefficient b3.

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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} What minimum annual income would an individual with a family size of 4 and 16 years of education need to attain a predicted 10,000 square foot home? 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} What minimum annual income would an individual with a family size of 4 and 16 years of education need to attain a predicted 10,000 square foot home?

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____________________ is a condition that exists when independent variables are correlated with one another.

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Life Expectancy An actuary wanted to develop a model to predict how long individuals will live.After consulting a number of physicians,she collected the age at death (y),the average number of hours of exercise per week (x1),the cholesterol level (x2),and the number of points that the individual's blood pressure exceeded the recommended value (x3).A random sample of 40 individuals was selected.The computer output of the multiple regression model is shown below. THE REGRESSION EQUATION IS y = 55.8 + 1.79x1 -0.021x2 -0.061x3 Predicter Coef StDev T Constant 55.8 11.8 4.729 1.79 0.44 4.068 -0.021 0.011 -1.909 -0.016 0.014 -1.143 S=9.47RSq=22.5%S = 9.47 \quad R - S q = 22.5 \% ANALYSIS OF VARIANCE Source of Variation Repressian 3 936 312 3.477 Error 36 3230 89.722 Total 39 4166 -{Life Expectancy Narrative} What is the adjusted coefficient of determination in this situation? What does this statistic tell you?

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If the value of the Durbin-Watson test statistic,d,satisfies the inequality d > 4 - dL,we conclude that positive first-order autocorrelation exists.

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Given that the Durbin-Watson test is conducted to test for positive first-order autocorrelation with α\alpha = .05,n = 20,and there are two independent variables in the model,the critical values for the test are dL = __________ and dU = __________,respectively.

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To use the Durbin-Watson test to test for negative first-order autocorrelation,the null hypothesis will be H0: ____________________ (there is/there is no)first-order autocorrelation.

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In testing the significance of a multiple regression model with three independent variables,the null hypothesis is H0:β1=β2=β3H _ { 0 } : \beta _ { 1 } = \beta _ { 2 } = \beta _ { 3 } .

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If the residuals in a regression analysis of time ordered data are not correlated,the value of the Durbin-Watson d statistic should be near ____________________.

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To test the validity of a multiple regression model,we test the null hypothesis that the regression coefficients are all zero by applying the:

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Senior Medical Students A professor of Anatomy wanted to develop a multiple regression model to predict the students' grades in her fourth-year medical course.She decides that the two most important factors are the student's grade point average in the first three years and the student's major.She proposes the model y = β\beta 0 + β\beta 1x1 + β\beta 2x2 + β\beta 3x3 + ε\varepsilon ,where y = Fourth-year medical course final score (out of 100),x1 = G.P.A.in first three years (range from 0 to 12),x2 = 1 if student's major is medicine and 0 if not,and x3 = 1 if student's major is biology and 0 if not.The computer output is shown below. THE REGRESSION EQUATION IS y = 9.14 + 6.73x1 + 10.42x2 + 5.16x3 Predictor Coef StDev T Constant 9.14 7.10 1.287 6.73 1.91 3.524 10.42 4.16 2.505 5.16 3.93 1.313 S=15.0RSq=44.2%S = 15.0 \quad R - S q = 44.2 \% ANALYSIS OF VARIANCE Source of Variation df SS MS F Regression 3 17098 5699.333 25.386 Error 96 21553 224.510 Total 99 38651 -In multiple regression analysis,the adjusted coefficient of determination is adjusted for the number of independent variables and the sample size.

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Life Expectancy An actuary wanted to develop a model to predict how long individuals will live.After consulting a number of physicians,she collected the age at death (y),the average number of hours of exercise per week (x1),the cholesterol level (x2),and the number of points that the individual's blood pressure exceeded the recommended value (x3).A random sample of 40 individuals was selected.The computer output of the multiple regression model is shown below. THE REGRESSION EQUATION IS y = 55.8 + 1.79x1 -0.021x2 -0.061x3 Predicter Coef StDev T Constant 55.8 11.8 4.729 1.79 0.44 4.068 -0.021 0.011 -1.909 -0.016 0.014 -1.143 S=9.47RSq=22.5%S = 9.47 \quad R - S q = 22.5 \% ANALYSIS OF VARIANCE Source of Variation Repressian 3 936 312 3.477 Error 36 3230 89.722 Total 39 4166 -{Life Expectancy Narrative} Is there enough evidence at the 5% significance level to infer that the model is useful in predicting length of life?

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Small values of the Durbin-Watson statistic d (d < 2)indicate a negative first-order autocorrelation.

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Life Expectancy An actuary wanted to develop a model to predict how long individuals will live.After consulting a number of physicians,she collected the age at death (y),the average number of hours of exercise per week (x1),the cholesterol level (x2),and the number of points that the individual's blood pressure exceeded the recommended value (x3).A random sample of 40 individuals was selected.The computer output of the multiple regression model is shown below. THE REGRESSION EQUATION IS y = 55.8 + 1.79x1 -0.021x2 -0.061x3 Predicter Coef StDev T Constant 55.8 11.8 4.729 1.79 0.44 4.068 -0.021 0.011 -1.909 -0.016 0.014 -1.143 S=9.47RSq=22.5%S = 9.47 \quad R - S q = 22.5 \% ANALYSIS OF VARIANCE Source of Variation Repressian 3 936 312 3.477 Error 36 3230 89.722 Total 39 4166 -{Life Expectancy Narrative} What is the coefficient of determination? What does this statistic tell you?

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Life Expectancy An actuary wanted to develop a model to predict how long individuals will live.After consulting a number of physicians,she collected the age at death (y),the average number of hours of exercise per week (x1),the cholesterol level (x2),and the number of points that the individual's blood pressure exceeded the recommended value (x3).A random sample of 40 individuals was selected.The computer output of the multiple regression model is shown below. THE REGRESSION EQUATION IS y = 55.8 + 1.79x1 -0.021x2 -0.061x3 Predicter Coef StDev T Constant 55.8 11.8 4.729 1.79 0.44 4.068 -0.021 0.011 -1.909 -0.016 0.014 -1.143 S=9.47RSq=22.5%S = 9.47 \quad R - S q = 22.5 \% ANALYSIS OF VARIANCE Source of Variation Repressian 3 936 312 3.477 Error 36 3230 89.722 Total 39 4166 -{Life Expectancy Narrative} Is there enough evidence at the 5% significance level to infer that the cholesterol level and the age at death are negatively linearly related?

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If the value of the Durbin-Watson statistic,d,satisfies the inequality dL \le d \le dU,where dL and dU are the critical values for d,then the test for positive first-order autocorrelation is inconclusive.

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Some of the requirements for the error variable in a multiple regression model are that the probability distribution is ____________________ with a mean of ____________________.

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Suppose a multiple regression analysis involving 25 data points has sz2=1.8s _ { z } ^ { 2 } = 1.8 and SSE = 36.Then,the number of the independent variables must be:

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

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