"What "standard deviation"? Typo: should have been "standard distribution"... Less colloquially: "a two-variable normal distribution." "What does "ellipse isn

"What "standard deviation"? Typo: should have been "standard distribution"... Less colloquially: "a two-variable normal distribution." "What does "ellipse isn't irregular" mean?" Eccentricity. Sorry `fer the double negative. "Kepler? The linked graph? How is this helpful in understanding what's going on?" If you take the scattered data and draw an ellipse containing a fixed probability (presumably represented with some confidence, by the data shown), the ellipse would be more eccentric for the same enclosed probability, the higher the correlation. It's a single statistic and is analogous to Kepler's 2nd law ("a line joining a planet and the Sun sweeps out equal areas during equal intervals of time."), except with probability rather than area... (To contain the same probability, you have to adjust the ellipse's size, while holding its enclosed probability constant, and accounting for the new eccentricity, which isn't under our control. If the area is fixed and the distance changes, solve for speed... I think visually. Alternatively, think V=IR.; if V is constant and R is known, solve for I.). The link was just illustrative of any such scatter plot. It was the best I could find, but I agree, it could have been better. I agree that the article is low on quantitative statistics though.