Problem-Solving and Data AnalysisMediumSpend that predicts a target from a fitted line
Problem-Solving and Data Analysis practice question
A line of best fit relating a shop's monthly advertising spend, x, in thousands of dollars, to its monthly sales, y, in thousands of dollars, is y = 1.5x + 10. According to the line, what advertising spend, in thousands of dollars, would predict sales of 70 thousand dollars?
Answer: 40
Set 1.5x + 10 = 70: 1.5x = 60, so x = 40.
Common wrong answers
- If you answered 115
- 115 is 1.5(70) + 10 — the sales predicted from a SPEND of 70, the reverse of what was asked.
- If you answered 46.67
- 46.67 is 70/1.5, forgetting to subtract the 10 first.
- If you answered 53.33
- 53.33 is (70 + 10)/1.5, adding the 10 instead of subtracting it.
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