Use paired measurements to describe an association or make a model-based prediction. A fitted line summarizes a trend; it does not force every observation to lie on the line.
Key Rules
Interpret slope as a predicted output change for one unit of input.
Substitute an input into the model to find its predicted output.
An association alone does not establish that one variable causes another.
Common Mistakes to Avoid
Reporting a prediction as an exact observed measurement.
Extrapolating far beyond the measured range without recognizing the uncertainty.
SAT Strategy Tips
→Read both axis labels and their units.
→Compare a point with the model to distinguish observed and predicted values.
Example Question
A model predicts plant height y, in centimeters, after x weeks by y = 12 + 3x. What height does it predict at 4 weeks?
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