Regression

Khan Academy:
 * 1) Squared Error of Regression Line
 * 2) Proof (Part 1) Minimizing Squared Error to Regression Line
 * 3) Proof (Part 3) Minimizing Squared Error to Regression Line
 * 4) Proof (Part 4) Minimizing Squared Error to Regression Line
 * 5) Regression Line Example
 * 6) Proof Part 2 Minimizing Squared Error to Line
 * 7) Second Regression Example
 * 8) Covariance and the Regression Line