What Fit Means - Linear Regression (Least Squares)

A line is controlled by an intercept and a slope. This lesson separates the displayed points from the later rule that chooses the line.

highlighted = computed this step

A line has parameters

A candidate line has intercept a and slope b. Choosing a and b selects one line from the family.

y=a+b x

Why fit means choose

Fit means choose a and b so the line matches the shown data by an exact rule. Fitting means choosing a and b for these points; it is not a capability claim.

\text{choose }a,b\text{ from shown data}

Summary

The plot shows only the data. The line has not been chosen yet.

\text{data first, line second}