Problem-Solving and Data AnalysisMediumInterpreting the slope of a line of best fit
Problem-Solving and Data Analysis practice question
A scatterplot shows the relationship between the number of kilometres x a car is driven in a week and the weekly fuel cost y in dollars. The line of best fit is y = 0.5x + 30. Which of the following is the best interpretation of the slope?
- A. Each additional kilometre driven is associated with an increase of about $0.50 in weekly fuel cost.Correct
- B. Each additional kilometre driven is associated with an increase of about $30 in weekly fuel cost.
- C. A car driven 0 kilometres has a fuel cost of $0.50.
- D. The car uses half a litre of fuel per kilometre.
Answer: A. Each additional kilometre driven is associated with an increase of about $0.50 in weekly fuel cost.
The slope is the change in y per unit change in x: $0.50 per kilometre.
Why the other answers are wrong
- B. Each additional kilometre driven is associated with an increase of about $30 in weekly fuel cost.
- $30 is the intercept.
- C. A car driven 0 kilometres has a fuel cost of $0.50.
- At 0 km the predicted cost is the intercept, $30.
- D. The car uses half a litre of fuel per kilometre.
- The model is in dollars, not litres.
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