Draw a scatter diagram (of 10 points) on a sheet of paper that represents a moderately positive correlation between the variables. Now drop your pencil at random on this scatter diagram.
(a) If you think of your pencil as a regression line, what aspect of the regression line are you changing as you move the pencil vertically on the paper?
(b) What aspect of the regression line are you changing as you twist, or rotate, your pencil?
(c) If you didn’t remember any of the equations for the slope and intercept, how could you tell if your pencil was forming the optimal regression line?