16Hit1600
Problem-Solving and Data AnalysisEasy–MediumPredicting from a line of best fit

Problem-Solving and Data Analysis practice question

For a set of data, the line of best fit is given by y = 1.8x + 6.

According to the model, what is the predicted value of y when x = 15?

  1. A. 10.8
  2. B. 27
  3. C. 33Correct
  4. D. 91.8

Answer: C. 33

Substitute 15 for x: y = 1.8(15) + 6 = 27 + 6 = 33.

Why the other answers are wrong

A. 10.8
10.8 is 1.8 times 6 — you multiplied the two constants together instead of substituting x. The 15 has to replace x.
B. 27
27 is 1.8(15); you stopped before adding the intercept. The model adds 6 to every prediction.
D. 91.8
You swapped the roles of the two numbers, computing 6(15) + 1.8. The coefficient of x is 1.8, and 6 is the constant added at the end.

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