3-minute lecture

Click on line.mp3 to open the sound recording in a new window.

Once the sound starts, switch back to this window.

To pause or rewind the lecture, switch to the sound window.

Press Move to start the demonstration. Press Curve to change to a curve.

Illustrates a basic idea about fitting a line to points: In a linear model, the effect of a change in X on Y is the same at all levels of X. The line has a constant slope of 0.1 in this example, so a difference of 100 in X makes a difference of 10 in Y, regardless of what X is.

The Move button makes the change in X and change in Y indicators move across the graph. Click again to stop the movement.
The Curve button shows a curved relationship between X and Y. Click it again to return to the linear relationship. In the curve model, a 100 difference in X makes a varying difference in Y. In this example, the Y difference gets smaller, then bigger, as X goes from 0 to 800.
The Line button switches you back to the line from the curve.