数据分析8(1).doc

Question 1
We modeled the gas mileage of 398 cars built in the 1970’s and early 1980’s using engine displacement (in cubic inches), year of manufacture in relation to 1970 (. 4 means the car was built in 1974; 12 means built in 1982, etc.), and manufacturing site (domestic to the USA = 0; foreign to the USA = 1). The regression output is provided below. Note that domestic is the reference level for manufacturing site.
Which of the following is the degrees of freedom associated with the p-value for site?
Your Answer
Score
Explanation
398
3
2
394
395
Inorrect

394=n−k−1=398−3−1
Total
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Question ExplanationThis question refers to the following learning objective(s): Note that the p-values associated with each predictor are conditional on other variables being included in the model, so they can be used to assess if a given predictor is significant, given that all others are in the model. These p-values are calculated based on a t distribution with n−k−1 degrees of freedom.
Question 2
We modeled the gas mileage of 398 cars built in the 1970’s and early 1980’s using engine displacement (in cubic inches), year of manufacture in relation to 1970 (. 4 means the car was built in 1974; 12 means built in 1982, etc.), and manufacturing site (domestic to the USA = 0; foreign to the USA = 1). The regression output is provided below. Note that domestic is the reference level for manufacturing site.
Which of the following is the correct predicted gas mileage (in miles per gallon) for a domestic car with an engine displacement of 350 cubic inches built in 1975?
Your Answer
Score
Explanation
−×350+×1975+
Inorrect

The year should be measured as years since 1970, and domestic is the reference level of site.
−×350+×1975
−×350+×5+
−×350+×5
Total
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Question ExplanationThis question refers to the following learni