Scatter Plots & Bivariate Data

What you’ll learn

• Read a fit line as $y=mx+b$: the slope is the predicted change in $y$ per unit of $x$, and a residual is actual minus predicted.
• Bivariate data pairs two quantitative variables so you can study how they change together.
• Scatter plots reveal direction, strength, clusters, gaps, and outliers before you choose any model.
• A line of best fit summarizes a linear trend; it simplifies data and should be judged by how close points fall.
• Positive association means both variables tend to increase together; negative means one tends to drop as the other rises.
• Two-way frequency tables organize counts for two categorical variables and help compare groups fairly.