SAT Math: Line of Best Fit
32+ practice questions in Praczo
The concept, explained
- 1
The line of best fit summarizes the trend in a scatterplot by minimizing overall distance from the line to data points.
- 2
The slope tells you the average change in y per one-unit increase in x — in context.
- 3
The y-intercept is the predicted value of y when x = 0 — interpret it carefully; it may not be meaningful for the specific scenario.
- 4
To make a prediction, substitute the given x-value into the equation and compute y. Inside the data range = interpolation (reliable); outside = extrapolation (less reliable).
- 5
The line does not pass through every point — it represents the general trend, not exact values.
- ✗ Treating the slope as a specific data point rather than an average rate: slope says "for each unit increase in x, y changes by [slope] on average."
- ✗ Using extrapolated predictions as if they were guaranteed — the further from the data range, the less reliable.
SAT-style practice
A scatterplot shows the relationship between hours of study (x) and test score (y). The line of best fit is y = 5x + 40. What does the slope represent?
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