Find the line that minimizes the sum of squared residuals (the red boxes). Move the line manually, then click "Fit OLS" to snap to the optimum.
Liney = 0 + 0·x
SSE (residual²)—
R²—
0
0.00
Why squared? Squaring residuals makes them positive and penalizes big misses more than small ones. The result has a closed-form optimum — no iteration needed — and matches the slope b = r·(σy/σx).