# Question #1f5c1

It's used in statistics. For each variable compute its variance S. Their ratio ${S}_{y} / {S}_{x}$ multiplied by the correlation (the relative variance of x and y) called $r$ is the $\beta$ of the regression, that is the slope of the regression line.
Take the temperature in your hometown between sunrise and noon. It increases. It also fluctuates on top of that increase. Plotting temperature as a function of x you would see points scattered around a straight line. That straight line is $\overline{y} = {b}_{0} + {b}_{1} x$