Lesson 13 of 20 · about 17 min

Least squares

Real data never lies exactly on a line, so the system "line through every point" has no solution. Least squares finds the line that misses by the least, measured as the total area of squares built on the misses. You'll shrink those squares by hand, see the exact answer, drag points to feel how an outlier pulls the line, and fit 60 years of real carbon dioxide measurements.