Linear Regression, geogebra demonstration
There are 5 points graphed below, together with the regression line that is the best linear fit to the 5 points. The coordinates of point E can be changed. To change the x-coordinate click and drag the point on the green horizontal bar. To change the y-coordinate, click and drag the point on the green vertical bar. Note the the regression line and the values for R and R2 change. R is the correlation coefficient, and R2 is the coefficient of determination.