Diagnostics: residual plots Feb 15 2019

Violations of assumptions

In rough order of importance:

Using the residuals to diagnose problems

Graphical versus formal inferential methods

Residual plots to examine

What to look for

An even width band vertically centered around zero as you move left to right (always put the residuals on the y-axis).

Points falling close to a straight line

Your turn: Part One

Handout (Charlotte will bring):

Part One Describe what you see in the residual plots that suggests a violation of assumptions.

Your turn: Part Two

Part Two The same five models are examined but in a random order, with a much smaller sample size. Can you match these diagnostics to those in Part Two??

Your turn: Part Three

Part Three Do you see any violations here?

Common problems and possible solutions