Repeated Measures ANOVA

Question 1

Repeated measures ANOVA

Answer 1

• Used when we have 3 or more within-subject conditions
• Similar to one-way independent ANOVA
• Looks at differences between means of 3+ conditions (like dependent t-test but for 3+ conditions)
• It tells us if there is a significant difference between the means, but not which means differ → post-hoc/planned contrasts test

Question 2

Repeated measures ANOVA by hand

Answer 2

• Same as one-way independent ANOVA except that we can make an adjustment for the fact we are using the same participants each time

Question 3

Repeated measures ANOVA assumptions

Answer 3

• All the usual assumptions of parametric testing
• Assumption of sphericity: assumption that the variance of differences between pairs of treatment level are equal
• In SPSS: Mauchly’s test
  
  • A non-significant test statistic indicates that the assumption has been met

Question 4

Repeated measures ANOVA SPSS output

Answer 4

Question 5

What do we do if the assumptions of sphericity is violated?

Answer 5

• Greenhouse-Geisser BUT
  
  • If G-G estimate is greater than .75, use Huynh-Feldt