ANCOVA

Question 1

ANCOVA

Answer 1

• analysis of co-variance
• to test for differences between group means when we know that an extraneous variable affects the outcome variable
• used to control known extraneous variables
• reduces error variance
• greater experimental control
• how variables interact

Question 2

Interactions

Answer 2

• show how the effects of one IV might depend on the effects of another
• are often more interesting than main effects

Question 3

Summary

Answer 3

• if you have a covariate, measure it and adjust
• ensure that your model is in the correct order
• understand the statistical models can be compared using statistics to determine the minimal adequate model