Exam 19: Multiple Regression

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Given the multiple linear regression equation  Given the multiple linear regression equation    = - 0.80 + 0.12 x _ { 1 } + 0.08 x _ { 2 }  , the value -0.80 is the  y  intercept. =0.80+0.12x1+0.08x2= - 0.80 + 0.12 x _ { 1 } + 0.08 x _ { 2 } , the value -0.80 is the yy intercept.

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A statistician wanted to determine whether the demographic variables of age, education and income influence the number of hours of television watched per week. A random sample of 25 adults was selected to estimate the multiple regression model y=β0+β1x1+β2x2+β3x3+εy = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + \varepsilon . Where: y = number of hours of television watched last week. x1x _ { 1 } = age. x2x _ { 2 } = number of years of education. X3X _ { 3 } = income (in $1000s). The computer output is shown below. THE REGRESSION EQUATION IS y=y = 22.3+0.41x10.29x20.12x322.3 + 0.41 x _ { 1 } - 0.29 x _ { 2 } - 0.12 x _ { 3 } Predictor Coef StDev Constant 22.3 10.7 2.084 0.41 0.19 2.158 -0.29 0.13 -2.231 -0.12 0.03 -4.00 S = 4.51 R-Sq = 34.8%. ANALYSIS OF VARIANCE Source of Variation df SS MS F Regression 3 227 75.667 3.730 Error 21 426 20.286 Total 24 653 Interpret the coefficient b2b _ { 2 } .

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Given the multiple linear regression equation, ŷ = b0 + b1x1 + b2x2, the value of b2 is the estimated average increase in y for a one unit increase in x2, whilst holding x1 constant.

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Pop-up coffee vendors have been popular in the city of Adelaide in 2013. A vendor is interested in knowing how temperature (in degrees Celsius) and number of different pastries and biscuits offered to customers impacts daily hot coffee sales revenue (in $00's). A random sample of 6 days was taken, with the daily hot coffee sales revenue and the corresponding temperature and number of different pastries and biscuits offered on that day, noted. Describe the following scatterplots. Pop-up coffee vendors have been popular in the city of Adelaide in 2013. A vendor is interested in knowing how temperature (in degrees Celsius) and number of different pastries and biscuits offered to customers impacts daily hot coffee sales revenue (in $00's). A random sample of 6 days was taken, with the daily hot coffee sales revenue and the corresponding temperature and number of different pastries and biscuits offered on that day, noted. Describe the following scatterplots.   Scatterplot of Daily hot coffee sales revenue vs Temperature   Scatterplot of Daily hot coffee sales revenue Pastries/biscuits   Residual scatterplot of Daily hot coffee sales revenue vs fitted values Scatterplot of Daily hot coffee sales revenue vs Temperature Pop-up coffee vendors have been popular in the city of Adelaide in 2013. A vendor is interested in knowing how temperature (in degrees Celsius) and number of different pastries and biscuits offered to customers impacts daily hot coffee sales revenue (in $00's). A random sample of 6 days was taken, with the daily hot coffee sales revenue and the corresponding temperature and number of different pastries and biscuits offered on that day, noted. Describe the following scatterplots.   Scatterplot of Daily hot coffee sales revenue vs Temperature   Scatterplot of Daily hot coffee sales revenue Pastries/biscuits   Residual scatterplot of Daily hot coffee sales revenue vs fitted values Scatterplot of Daily hot coffee sales revenue Pastries/biscuits Pop-up coffee vendors have been popular in the city of Adelaide in 2013. A vendor is interested in knowing how temperature (in degrees Celsius) and number of different pastries and biscuits offered to customers impacts daily hot coffee sales revenue (in $00's). A random sample of 6 days was taken, with the daily hot coffee sales revenue and the corresponding temperature and number of different pastries and biscuits offered on that day, noted. Describe the following scatterplots.   Scatterplot of Daily hot coffee sales revenue vs Temperature   Scatterplot of Daily hot coffee sales revenue Pastries/biscuits   Residual scatterplot of Daily hot coffee sales revenue vs fitted values Residual scatterplot of Daily hot coffee sales revenue vs fitted values

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Pop-up coffee vendors have been popular in the city of Adelaide in 2013. A Pop-up coffee vendor is interested in knowing how temperature (in degrees Celsius) and number of different pastries and biscuits offered to customers, impacts daily hot coffee sales revenue (in $00's). A random sample of 6 days was taken, with the daily hot coffee sales revenue and the corresponding temperature and number of different pastries and biscuits offered on that day, noted. Excel output for a multiple linear regression is given below: Coffee sales revenue Temperature Pastries/biscuits 6.5 25 7 10 17 13 5.5 30 5 4.5 35 6 3.5 40 3 28 9 15  Pop-up coffee vendors have been popular in the city of Adelaide in 2013. A Pop-up coffee vendor is interested in knowing how temperature (in degrees Celsius) and number of different pastries and biscuits offered to customers, impacts daily hot coffee sales revenue (in $00's). A random sample of 6 days was taken, with the daily hot coffee sales revenue and the corresponding temperature and number of different pastries and biscuits offered on that day, noted. Excel output for a multiple linear regression is given below:  \begin{array} { | c | c | r | }  \hline \text { Coffee sales revenue } & \text { Temperature } & \text { Pastries/biscuits } \\ \hline 6.5 & 25 & 7 \\ \hline 10 & 17 & 13 \\ \hline 5.5 & 30 & 5 \\ \hline 4.5 & 35 & 6 \\ \hline 3.5 & 40 & 3 \\ \hline 28 & 9 & 15 \\ \hline \end{array}    a. Write down the multiple regression model. b. Interpret the coefficient of Temperature. c. Interpret the coefficient of Pastries/biscuits. a. Write down the multiple regression model. b. Interpret the coefficient of Temperature. c. Interpret the coefficient of Pastries/biscuits.

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

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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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An economist wanted to develop a multiple regression model to enable him to predict the annual family expenditure on clothes. After some consideration, he developed the multiple regression model: y=β0+β1x1+β2x2+β3x3+εy = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + \varepsilon . Where: y = annual family clothes expenditure (in $1000s) x1x _ { 1 } = annual household income (in $1000s) x2x _ { 2 } = number of family members X3X _ { 3 } = number of children under 10 years of age The computer output is shown below. THE REGRESSION EQUATION IS y=1.74+0.091x1+0.93x2+0.26x3y=1.74+0.091 x_{1}+0.93 x_{2}+0.26 x_{3} Predictor Coef StDev Constant 1.74 0.630 2.762 0.091 0.025 3.640 0.93 0.290 3.207 0.26 0.180 1.444 S=2.06RSq=59.6%\mathrm { S } = 2.06 \quad \mathrm { R } - \mathrm { Sq } = 59.6 \% ANALYSIS OF VARIANCE Source of Variation df SS MS F Regression 3 288 96 22.647 Error 46 195 4.239 Total 49 483 Test at the 10% significance level to determine whether annual household income and annual family clothes expenditure are linearly related.

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A multiple regression model has the form ŷ = b0 + b1x1 + b2x2. Which of the following best describes b2?

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In order to test the significance of a multiple regression model involving 4 independent variables and 30 observations, the number of degrees of freedom for the numerator and denominator for the critical value of F are 4 and 26, respectively.

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Multiple linear regression is used to estimate the linear relationship between one dependent variable and more than one independent variables.

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When the independent variables are correlated with one another in a multiple regression analysis, this condition is called:

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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 ( x1x _ { 1 } ), the cholesterol level ( x2x _ { 2 } ), and the number of points by which the individual's blood pressure exceeded the recommended value ( X3X _ { 3 } ). A random sample of 40 individuals was selected. The computer output of the multiple regression model is shown below: THE REGRESSION EQUATION IS y=y = 55.8+1.79x10.021x20.016x355.8 + 1.79 x _ { 1 } - 0.021 x _ { 2 } - 0.016 x _ { 3 } Predictor 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 = 9.47 R-Sq = 22.5%. ANALYSIS OF VARIANCE Source of Variation df SS MS F Regression 3 936 312 3.477 Error 36 3230 89.722 Total 39 4166 Is there enough evidence at the 1% significance level to infer that the average number of hours of exercise per week and the age at death are linearly related?

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The computer output for the multiple regression model y=β0+β1x1+β2x2+ξy = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \xi is shown below. However, because of a printer malfunction some of the results are not shown. These are indicated by the boldface letters a to i. Fill in the missing results (up to three decimal places). Predictor Coef StDev Constant a 0.120 3.18 0.068 b 3.38 0.024 0.010 c S = d R-Sq = e. ANALYSIS OF VARIANCE Source of Variation df SS MS F Regression 2 7.382 g i Error 22 f h Total 24 7.530

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An estimated multiple regression model has the form ŷ = 100 − 2x1 + 9x2. As x1 increases by 1 unit while holding x2 constant, which of the following best describes the change in y?

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A statistician wanted to determine whether the demographic variables of age, education and income influence the number of hours of television watched per week. A random sample of 25 adults was selected to estimate the multiple regression model y=β0+β1x1+β2x2+β3x3+εy = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } + \beta _ { 3 } x _ { 3 } + \varepsilon . Where: y = number of hours of television watched last week. x1x _ { 1 } = age. x2x _ { 2 } = number of years of education. X3X _ { 3 } = income (in $1000s). The computer output is shown below. THE REGRESSION EQUATION IS y=y = 22.3+0.41x10.29x20.12x322.3 + 0.41 x _ { 1 } - 0.29 x _ { 2 } - 0.12 x _ { 3 } Predictor Coef StDev Constant 22.3 10.7 2.084 0.41 0.19 2.158 -0.29 0.13 -2.231 -0.12 0.03 -4.00 S = 4.51 R-Sq = 34.8%. ANALYSIS OF VARIANCE Source of Variation df SS MS F Regression 3 227 75.667 3.730 Error 21 426 20.286 Total 24 653 Is there sufficient evidence at the 1% significance level to indicate that hours of television watched and age are linearly related?

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A multiple regression model has the form ŷ = 24 - 0.001x1 + 3x2. As x1 increases by 1 unit, holding x2x _ { 2 } constant, the value of y is estimated to decrease by 0.001units, on average.

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Which of the following measures can be used to assess a multiple regression model's fit?

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In multiple regression, and because of a commonly occurring problem called multicollinearity, the t-tests of the individual coefficients may indicate that some independent variables are not linearly related to the dependent variable, when in fact they are.

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Which of the following best describes the range of the coefficient of multiple determination?

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