Problem-Solving and Data AnalysisMediumChange predicted by a linear model
Problem-Solving and Data Analysis practice question
A model for a company's sales y, in thousands of dollars, against its advertising spending x, in thousands of dollars, is y = 2.5x + 10. According to the model, an increase of 4 thousand dollars in advertising increases predicted sales by how many thousand dollars?
Answer: 10
The slope 2.5 is the change in y per unit of x, so 4 units of x give 4 × 2.5 = 10.
Common wrong answers
- If you answered 14
- 14 adds 4 to 10.
- If you answered 20
- 20 evaluates y at x = 4 instead of finding the change.
- If you answered 2.5
- 2.5 is the change for one unit, not four.
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