Exam 17: Multiple Regression

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If all the points for a multiple regression model with two independent variables were right on the regression plane, then the coefficient of determination would equal:

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The coefficient of determination ____________________ for degrees of freedom takes into account the sample size and the number of independent variables when assessing model fit.

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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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How do you go about checking for multicollinearity?

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The total variation in y in a regression model will never exceed the regression sum of squares (SSR).

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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 multiple regression model has the form y^=8+3x1+5x24x3\hat { y } = 8 + 3 x _ { 1 } + 5 x _ { 2 } - 4 x _ { 3 } . As x3 increases by one unit, with x1 and x2 held constant, the y on average is expected to:

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Most statistical software print a second R2 statistic, called the coefficient of determination adjusted for degrees of freedom, which has been adjusted to take into account the sample size and the number of independent variables.

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NARRBEGIN: Life Expectancy 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 predictor Coef SUDev 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 Repression 3 936 312 3.477 Error 36 3230 89.722 Tatol 39 4166 NARREND -{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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A multiple regression model has the form: y^=5.25+2x1+6x2\hat { y } = 5.25 + 2 x _ { 1 } + 6 x _ { 2 } . As x2 increases by one unit, holding x1 constant, then the value of y will increase by:

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When there is more than one independent variable in a regression model, we refer to the graphical depiction of the equation as a(n) ____________________ rather than as a straight line.

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

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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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NARRBEGIN: Life Expectancy 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 predictor Coef SUDev 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 Repression 3 936 312 3.477 Error 36 3230 89.722 Tatol 39 4166 NARREND -{Life Expectancy Narrative} Is there sufficient evidence at the 5% significance level to infer that the number of points that the individual's blood pressure exceeded the recommended value and the age at death are negatively linearly related?

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In a multiple regression analysis involving 40 observations and 5 independent variables, the following statistics are given: Total variation in y = 350 and SSE = 50. Then, the coefficient of determination is:

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The coefficient of determination ranges from:

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Test the hypotheses H0: no first-order autocorrelation vs. H1: first-order autocorrelation, given that: Durbin-Watson Statistic d = 1.89, n = 28, k = 3, and α\alpha = 0.05.

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Multicollinearity is present when there is a high degree of correlation between the dependent variable and any of the independent variables.

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The Durbin-Watson test allows the statistics practitioner to determine whether there is evidence of first-order autocorrelation.

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Large values of the Durbin-Watson statistic d (d > 2) indicate a positive first-order autocorrelation.

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