Repeated Measures ANOVAs

Question 1

Why is repeated measures ANOVA needed?

Answer 1

• PPs contribute multiple data points

- Data is not independent

Question 2

What are the benefits of repeated measures?

Answer 2

• Sensitivity (unsystematic variance is reduced)

- Economy (fewer PPs needed)

Question 3

What are problems with repeated measures?

Answer 3

• Scores across conditions correlate because there’s the same PPs in all conditions (violating independence assumption)

Question 4

What is the sphericity assumption?

Answer 4

• Tells us whether the variance between groups is roughly the same

Question 5

How do we measure sphericity?

Answer 5

Mauchly’s test

Question 6

How do we know if the sphericity assumption has been met?

Answer 6

p>0.05

Question 7

What does sphericity argue?

Answer 7

That the variance in the differences between conditions is equal across participants

Question 8

How many levels does sphericity need?

Answer 8

More than 2 - only applies when you have more than 2 levels of your IV

Question 9

What estimates of sphericity are there?

Answer 9

• Greenhouse-Geisser
• Huynh-Feldt Estimate
• Lower Bound

Question 10

What is Within Subjects Variance? (SSw)

Answer 10

How much people vary within themselves between conditions

Question 11

How do we work out the within subjects degrees of freedom? (dfW)

Answer 11

• df per person = no. of conditions - 1

- Add up across PPs

Question 12

What post-hoc test do we usually use for repeated measures ANOVAs?

Answer 12

Bonferroni

Question 13

What is a mixed design?

Answer 13

Within and Between subject IVs