Sxx Variance Formula |best|

"Bingo," Jonah said, capping the marker. "You can't estimate the slope of a hill if you're only standing on one

Yes, since it’s a sum of squares. Zero only if all ( x_i ) are identical. Sxx Variance Formula

Suppose for a regression:

is essentially an "un-normalized" variance. To transform this absolute measure into an average measure of spread, it is divided by the degrees of freedom ( The average squared deviation. "Bingo," Jonah said, capping the marker

[ r = \fracS_xy\sqrtS_xx S_yy ]