Problem-Solving and Data AnalysisMediumResidual from a line of best fit
Problem-Solving and Data Analysis practice question
A line of best fit for a scatterplot is y = 2.5x + 10. One data point has x = 8 and y = 27. What is the residual (actual y minus predicted y) for that point?
Answer: -3
Predicted y = 2.5(8) + 10 = 30. Residual = 27 − 30 = −3.
Common wrong answers
- If you answered 3
- 3 reverses the subtraction (predicted minus actual).
- If you answered 7
- 7 comes from 27 − 20, forgetting the +10 in the prediction.
- If you answered 30
- 30 is the predicted value, not the residual.
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