The following applet lets you graph points to see if you can discover the trend and the line of best fit. The line of best fit is listed as a slope-intercept equation.

Instructions

1. Add a data point by clicking in the white area.
2. To move a data point, hold down shift and click and drag it to a new location.
3. To remove a data point, hold down control and click on the point.
4. When you have plotted several points, press Show Line to see the line of best fit.

Line of Best Fit

What happens to the correlation when some data points are outside of the trend?  These data points are called outliers.

Move one of your points outside of the trend line area to see what happens to the line.