The fitted line is chosen so vertical squared residuals are as small as possible—standard ordinary least squares (OLS) for simple regression.

b tells how much ŷ changes per unit increase in x; a anchors the line at x = 0 (only meaningful if x = 0 is in-range for your study).

r measures linear correlation between x and y. It is omitted when y has no variation (perfect horizontal fit).

In simple linear regression, R² equals r² when r is defined, summarizing how much variability in y is captured by the linear model.

The regression line always passes through (x̄, ȳ)—a useful check when plotting by hand or verifying software output.

Pair with our linear regression and R² tools when you need fuller tables, or with variance when discussing spread around the mean.