Scatterplots & Line of Fit at the 700-800 Level

At this tier the arithmetic is trivial. What is tested is whether you know exactly what a line of best fit claims — and, more often, what it does not claim.

Six archetypes cover the bank. The residual, with its sign intact: residual $=$ actual $-$ predicted, positive means above the line, and hard items run it backwards as actual $=$ predicted $+$ residual. Slope and intercept as sentences, always phrased as associated with rather than causes. Extrapolation beyond the data — a model built from cars 1 to 8 years old says nothing reliable about a 15-year-old car, and often predicts something impossible as a confirming clue. , asking when they are equal, which changes faster, or which starts higher. , decided by residual magnitudes and never by their signed sum. : a point at a typical raises the intercept and barely moves the slope, while a point at an extreme can swing the slope.