Video: Lines, curves and smoothers [4 min]

In this video, we discuss putting trends onto scatterplots using software.

(See also the Review Questions following the movie)

[Illustrated transcript (pdf)]

After you’ve watched this video, you should be able to answer these questions:

• What shapes can be captured by each of linear, quadratic and cubic trend curves?
• What advantage does a smoother have over quadratic or cubic curves?
• Why shouldn’t we take the behaviour of flexible trend curves at the right and left-hand edges of the plot too seriously?
• If you ask iNZight, or most standard software, to put a curve of a particular type onto the scatterplot (e.g. a quadratic), how does it choose which curve of this type to draw?