Question

In: Statistics and Probability

The data below was collected from manufacturer advertisements of their vehicles horsepower and highway gas mileage...

The data below was collected from manufacturer advertisements of their vehicles horsepower and highway gas mileage (mpg.). Use this data to answer the following questions.

x 158 250 340 350 390 190 220
y 33 28 15 17 11 35 42



1. Find the the correlation coefficient. Round your final answer to four decimal places.
r=r=  


2. Write the regression equation below. Round all numbers to four decimal places.
ˆy=y^=


3. Using the data shown above,predict the the highway gas mileage (mpg) for a car that has a horsepower of 225. Round your final answer to two decimal places.



4. What percentage of variation in highway gas mileage (mpg) can be explained by horsepower? Round your final answer to two decimal places.
%%

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Expert Solution

The statistical software output for this problem is:

Simple linear regression results:
Dependent Variable: y
Independent Variable: x
y = 57.987438 - 0.11849951 x
Sample size: 7
R (correlation coefficient) = -0.90396077
R-sq = 0.81714508
Estimate of error standard deviation: 5.4656445

Parameter estimates:

Parameter Estimate Std. Err. Alternative DF T-Stat P-value
Intercept 57.987438 7.1042425 ? 0 5 8.1623675 0.0004
Slope -0.11849951 0.0250689 ? 0 5 -4.7269528 0.0052


Analysis of variance table for regression model:

Source DF SS MS F-stat P-value
Model 1 667.4908 667.4908 22.344082 0.0052
Error 5 149.36635 29.87327
Total 6 816.85714


Predicted values:

X value Pred. Y s.e.(Pred. y) 95% C.I. for mean 95% P.I. for new
225 31.325049 2.3676322 (25.238857, 37.411241) (16.013582, 46.636516)

Hence,

1. Correlation coefficient = -0.9040

2. Regression equation:

= 57.9874 - 0.1185x

3. Predicted gas mileage = 31.3250

4. Percent of variation explained = 81.71%


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