Exam 7: Linear Regression

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A golf ball is dropped from 15 different heights (in cm)and the height of the bounce is recorded (in cm).The regression analysis gives the model  bounce ^=0.2+0.75\hat{\text { bounce }} = - 0.2 + 0.75 drop.A golf ball dropped from 61 cm bounced a height whose residual is -1.8 cm.What is the bounce height?

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A forester would like to know how big a maple tree might be at age 50 years.She gathers data from some trees that have been cut down,and plots the diameters (in inches)of the trees against their ages (in years).First she makes a linear model.The scatterplot and residuals plot are shown.Do you think the linear model is appropriate? Explain. A forester would like to know how big a maple tree might be at age 50 years.She gathers data from some trees that have been cut down,and plots the diameters (in inches)of the trees against their ages (in years).First she makes a linear model.The scatterplot and residuals plot are shown.Do you think the linear model is appropriate? Explain.    A forester would like to know how big a maple tree might be at age 50 years.She gathers data from some trees that have been cut down,and plots the diameters (in inches)of the trees against their ages (in years).First she makes a linear model.The scatterplot and residuals plot are shown.Do you think the linear model is appropriate? Explain.

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A random sample of 150 yachts sold in the Canada last year was taken.A regression analysis to predict the price (in thousands of dollars)from length (in metres)was completed.A linear model is appropriate.What are the units of the slope?

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A sociology student does a study to determine whether people who exercise live longer.He claims that someone who exercises 7 days a week will live 15 years longer than someone who doesn't exercise at all.

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When checking the "Straight Enough" condition,which is the best graph to look at?

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The relationship between the price of yachts (y)and their length (x)is analyzed.The mean length was 41 metres with a standard deviation of 11.The mean price was $84,000 with a standard deviation of 14,000.The correlation between the price and the length was 0.41.

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The relationship between the number of games won during one season by an NHL team and the average attendance at their home games is analyzed.A regression analysis to predict the average attendance from the number of games won gives the model  attendance ^=2100+187\hat{\text { attendance }} = - 2100 + 187 wins.Predict the average attendance of a team with 400 wins.Explain any possible problems with this prediction.

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=+ 10 5 ? ? -0.8 =200-2

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A random sample of 150 yachts sold in Canada last year was taken.A regression to predict the price (in thousands of dollars)from length (in metres)has an R2=18.3%\mathrm { R } ^ { 2 } = 18.3 \% What is correlation between length and price?

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A golf ball was dropped from 8 different heights.The drop height and the bounce height were recorded. Drop Height () Bounce Height () 96 73 84 65 72 55 60 46 48 38 36 29 24 19 12 8

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=+ 3.0 1.2 ? 120 ? =-120+60

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A golf ball is dropped from 15 different heights (in cm)and the height of the bounce is recorded (in cm).The regression analysis gives the model  bounce ^=0.3+0.74\hat{\text { bounce }} = 0.3 + 0.74 drop.A golf ball dropped from 61 cm bounced 46.44 cm.What is the residual for this bounce height?

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The relationship between the number of games won by an NHL team and the average attendance at their home games is analyzed.A regression analysis to predict the average attendance from the number of games won gives the model  attendance ^=2600+225\hat{\text { attendance }} = - 2600 + 225 wins.One team averaged 14,865 fans at each game and won 49 times.Calculate the residual for this team and explain what it means.

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The relationship between the number of games won by an NHL team and the average attendance at their home games is analyzed.A regression to predict the average attendance from the number of games won has an r=0.79\mathrm { r } = 0.79 Interpret this statistic.

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If the linear correlation between shoe size and height is 0.758 and Dave is 2 standard deviations above the mean in shoe size,what would you predict is Dave's height with respect to the mean height?

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Doctors studying how the human body assimilates medication inject some patients with penicillin,and then monitor the concentration of the drug (in units/cc)in the patients' blood for seven hours.First they tried to fit a linear model.The regression analysis and residuals plot are shown.Is that estimate likely to be accurate,too low,or too high? Explain. Dependent variable is:                  Concentration No Selector R squared =90.8%= 90.8 \% \quad R squared (adjusted) =90.6%= 90.6 \% s=3.472s = 3.472 with 432=4143 - 2 = 41 degrees of freedom Source Sum of Squares df Mean Square F-ratio Regression 4900.55 1 4900.55 407 Residual 494.199 41 12.0536 Variable Coefficient s.e. of Coeff t-ratio prob Constant 40.3266 1.295 31.1 S 0.0001 Time -5.95956 0.2956 -20.2 S 0.0001  Doctors studying how the human body assimilates medication inject some patients with penicillin,and then monitor the concentration of the drug (in units/cc)in the patients' blood for seven hours.First they tried to fit a linear model.The regression analysis and residuals plot are shown.Is that estimate likely to be accurate,too low,or too high? Explain. Dependent variable is:                  Concentration No Selector R squared  = 90.8 \% \quad  R squared (adjusted)  = 90.6 \%   s = 3.472  with  43 - 2 = 41  degrees of freedom  \begin{array} { l l r r r } \text { Source } & \text { Sum of Squares } & \text { df } & \text { Mean Square } & \text { F-ratio } \\ \text { Regression } & 4900.55 & 1 & 4900.55 & 407 \\ \text { Residual } & 494.199 & 41 & 12.0536 & \end{array}    \begin{array} { l l l r l } \text { Variable } & \text { Coefficient } & \text { s.e. of Coeff } & \text { t-ratio } & \text { prob } \\ \text { Constant } & 40.3266 & 1.295 & 31.1 & \text { S } 0.0001 \\ \text { Time } & - 5.95956 & 0.2956 & - 20.2 & \text { S } 0.0001 \end{array}

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The relationship between the number of games won by an NHL team (x)and the average attendance at their home games (y)is analyzed.The mean number of games won was 70 with a standard deviation of 16.The mean attendance was 6993 with a standard deviation of 1400.The correlation between the games won and attendance was 0.47.

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A golf ball is dropped from 15 different heights (in cm)and the height of the bounce is recorded (in cm.)The regression analysis gives the model  bounce ^=0.1+0.70\hat{\text { bounce }} = - 0.1 + 0.70 drop.Predict the height of the bounce if dropped from 64 cm.

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A random sample of 150 yachts sold in Canada last year was taken.A regression to predict the price (in thousands of dollars)from length (in feet)has an R2\mathrm { R } ^ { 2 } = 19.00%.What would you predict about the price of the yacht whose length was one standard deviation above the mean?

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