Exam 10: Correlation and Regression

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The residual is the difference between the ____________________ and the ___________________.

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Given the linear correlation coefficient r and the sample size n, determine the critical values of r_ and use your finding to state whether or not the given r represents a significant linear Correlation. Use a significance level of 0.05. r=0.543,n=25r = 0.543 , n = 25

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Find the value of the linear correlation coefficient r. The paired data below consist of the_ costs of advertising (in thousands of dollars)and the number of products sold (in thousands). Cost 9 2 3 4 2 5 9 10 Number 85 52 55 68 67 86 83 73

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Use computer software to find the multiple regression equation. Can the equation be used for prediction? An anti-smoking group used data in the table to relate the carbon monoxide( CO) Of various brands of cigarettes to their tar and nicotine (NIC)content. CO TAR NIC 15 1.2 16 15 1.2 16 17 1.0 16 6 0.8 9 1 0.1 1 8 0.8 8 10 0.8 10 17 1.0 16 15 1.2 15 11 0.7 9 18 1.4 18 16 1.0 15 10 0.8 9 7 0.5 5 18 1.1 16

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For the data below, determine the value of the linear correlation coefficient r between y and X₂. x 1.2 2.7 4.4 6.6 9.5 y 1.6 4.7 9.9 24.5 39.0

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Construct a scatterplot for the given data._ \begin{tabular} { c | l l l l l l l c } xx & 0.330.33 & 0.920.92 & 0.360.36 & 0.290.29 & 0.09- 0.09 & 0.970.97 & 0.390.39 & 0.30.3 \\ \hline yy & 0.50.5 & 0.490.49 & 0.080.08 & 0.270.27 & 0.13- 0.13 & 0.440.44 & 0.950.95 & 0.09- 0.09 \end{tabular}

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A regression equation is obtained for a set of data. After examining a scatter diagram, the_ researcher notices a data point that is potentially an influential point. How could she confirm that this data point is indeed an influential point?

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Suppose you will perform a test to determine whether there is sufficient evidence to support a claim of a linear correlation between two variables. Find the critical values of r given the Number of pairs of data n and the significance level α\alpha n=14,α=0.01n = 14 , \alpha = 0.01

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Use computer software to find the multiple regression equation. Can the equation be used for_ prediction? A wildlife analyst gathered the data in the table to develop an equation to predict The weights of bears. He used WEIGHT as the dependent variable and CHEST, LENGTH, And SEX as the independent variables. For SEX, he used male=1 and female=2. WEIGHT CHEST LENGTH SEX 344 45.0 67.5 1 416 54.0 72.0 1 220 41.0 70.0 2 360 49.0 68.5 1 332 44.0 73.0 1 140 32.0 63.0 2 436 48.0 72.0 1 132 33.0 61.0 2 356 48.0 64.0 2 150 35.0 59.0 1 202 40.0 63.0 2 365 50.0 70.5 1 A) WEIGHT =196+2.35= 196 + 2.35 CHEST +3.40LENGTH+25SEX+ 3.40 \mathrm { LENGTH } + 25 \mathrm { SEX } ; Yes, because the R2R ^ { 2 } is high. B) WEIGHT =320+10.6CHEST+7.3LENGTH10.7SEX= - 320 + 10.6 \mathrm { CHEST } + 7.3 \mathrm { LENGTH } - 10.7 \mathrm { SEX } ; Yes, because the PP -value is high. C) WEIGHT =442.6+12.1= - 442.6 + 12.1 CHEST + 3.6LENGTH 23.8- 23.8 SEX; Yes, because the adjusted R2R ^ { 2 } is high. D) WEIGHT =442.6+12= 442.6 + 12 .1CHEST +4.2+ 4.2 LENGTH 21- 21 SEX; Yes, because the PP -value is low.

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The following residual plot is obtained after a regression equation is determined for a set of data. Does the residual plot suggest that the regression equation is a bad model? Why or why not? The following residual plot is obtained after a regression equation is determined for a set of data. Does the residual plot suggest that the regression equation is a bad model? Why or why not?

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When testing to determine if correlation is significant, we use the hypotheses H0:ρ=0H _ { 0 } : \rho = 0 H1:ρ0H _ { 1 } : \rho \neq 0 What does the symbol ρ\rho represent? Explain the meaning of the null and altemative hypotheses.

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Define the terms predictor variable and response variable. Give examples for each._

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Use computer software to find the best multiple regression equation to explain the variation in the dependent variable, Y, in terms of the independent variables, X1,X2,X3X _ { 1 } , X _ { 2 } , X _ { 3 } Y 456 9896 29.1 1 421 9680 42.3 2 653 10449 29.8 3 573 10811 26.0 4 CORRELATION COEFFICIENTS 546 10014 34.3 5 499 10293 22.7 6 Y/=0.509 504 9413 24.2 7 Y/=0.280 611 9860 31.6 8 Y/ =0.930 646 9782 25.6 9 789 12139 37.9 10 COEFFICIENTS OF DETERMINATION 773 12166 33.9 11 753 9976 37.4 12 Y/ =0.259 852 10645 27.0 13 YI =0.079 755 9738 31.5 14 Y/=0.864 815 9933 39.9 15 Y/ ,=0.880 902 10132 25.3 16 Y/ ,,=0.884 986 11145 30.4 17 909 9775 32.7 18 945 9549 35.0 19 866 10077 33.8 20 1178 11550 29.4 21 1230 10600 37.1 22 1207 11280 42.9 23 968 12100 32.2 24 1118 12420 30.5 25

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A(n)___________________________ is a point lying far away from other data points on a scatterplot.

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Describe what scatterplots are and discuss the importance of creating scatterplots._

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Use computer software to find the best multiple regression equation to explain the variation in the dependent variable, Y , in terms of the independent variables, X1,X2,X3X _ { 1 } , X _ { 2 } , X _ { 3 } Y 15 1.2 16 15 1.2 16 CORRELATION COEFFICIENT 17 1.0 16 Y/=0.886 6 0.8 9 Y/=0.965 1 0.1 1 8 0.8 8 10 0.8 10 COEFFICIENTS OF DETERMINATION 17 1.0 16 15 1.2 15 11 0.7 9 18 1.4 18 16 1.0 15 =0.932 10 0.8 9 =0.943 7 0.5 5 18 1.1 16

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Given the linear correlation coefficient r and the sample size n, determine the critical values of_ r and use your finding to state whether or not the given r represents a significant linear Correlation. Use a significance level of 0.05. r=0.816,n=5r = - 0.816 , n = 5

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Use computer software to find the best multiple regression equation to explain the variation in_ the dependent variable, Y, in terms of the independent variables, X1,X2,X3X _ { 1 } , X _ { 2 } , X _ { 3 } Y 98.6 87.4 108.5 101.2 97.6 110.1 102.4 96.7 110.4 CORRELATION COEFFICIENTS 100.9 98.2 104.3 102.3 99.8 107.2 Y/=0.850 101.5 100.5 105.8 Y=0.742 101.6 103.2 107.8 101.6 107.8 103.4 99.8 96.6 102.7 COEFFICIENT OF DETERMINATION 100.3 88.9 104.1 97.6 75.1 99.2 97.2 76.9 99.7 97.3 84.6 102.0 96.0 90.6 94.3 99.2 103.1 97.7 100.3 105.1 101.1 100.3 96.4 102.3 104.1 104.4 104.4 105.3 110.7 108.5 107.6 127.1 111.3

(Multiple Choice)
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The table below shows the population of a city (in millions)in each year during the period 2010-2015. Using the number of years since 2010 as the independent variable, find the regression equation of the best model. Assume that the model is to be used only for the scope of the given data, and consider only linear, quadratic, logarithmic, exponential, and power models. Include the type of model and the equation for the model you find. Year 2010 2011 2012 2013 2014 2015 Population(millions) 1.08 1.37 1.68 2.19 2.73 3.34

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Find the coefficient of determination, given that the value of the linear correlation coefficient,_ r, is 0.738.

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