Scatterplots and Lines of Best Fit

SAT Math · Axiom Academy

Scatter Plots & Lines of Best Fit Interpret correlation and make predictions from linear relationships A scatter plot displays the relationship between two quantitative variables. Each point represents a pair of values (x, y), showing how one variable relates to another. Correlation describes the direction and strength of the relationship between two variables. As x increases, y increases. Points trend upward from left to right. Example: Hours studied vs. test score As x increases, y decreases. Points trend downward from left to right. Example: Temperature vs. hot chocolate sales No clear relationship. Points scattered randomly with no pattern. Example: Shoe size vs. favorite color Example 1: Identifying Correlation Type A scatter plot shows the relationship between study hours (x) and test scores (y). The points show a clear upward trend. Answer: This is a positive correlation. Generally, students who study more score higher on the test. Correlation also has strength—how tightly the points cluster around a line. Strong: Points closely follow a line (little scatter) Moderate: Points generally follow a trend but with some variation Weak: Points are more scattered; the trend is less obvious A line of best fit (or regression line) is a straight line that best represents the relationship between two variables. It passes through or near the points to show the overall trend. Example 2: Line of Best Fit Equation A line of best fit for a scatter plot has the equation y = 2x + 3 .

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