Two Factor Anova

Question 1

Tell me about a two-factor anova analysis

Answer 1

Two factor analysis:
1) Characterise the overall variability of the data
2) Look each condition itself (start with mean of condition 1, mean of condition 2). How far is the mean of each condition from the grand mean? This is the between-groups variability – a measure of how far the means of the individual groups are from the grand mean, and this would be bigger if the manipulation is having a greater effect
3) Variation in groups where people had the exact same manipulation cannot be due to the experimental manipulation.

Question 2

What is the difference in f values between a single factor and two factor ANOVA?

Answer 2

For single factor – you calculated a single F value. The bigger = more likely results statistically significant.

With 2 factor = we get 3 F values. One for the effect of one thing, one for the effect of the other thing and one for the interaction of those 2.

• There is still a between groups component and some noise group variability from the within groups.
• There are more things that can be significant and it can be more difficult to think about it.
• You could have 3 levels of the 1 factor and 7 levels of the other factor. So you have 21 conditions in total.

Question 3

Assumptions of ANOVA
What are assumptions of between participants ANOVA?

Answer 3

• Random and independent samples
• Normally distributed
• Equal population variances

Question 4

What are assumptions of within participants ANVOA?

Answer 4

• Random and independent samples
• Normality
• Sphericity

Question 5

What happens to the null if we have a significant ANOVA?

Answer 5

We reject the null hypothesis

Question 6

What does a graph look like when: there are no main affects or interactions (all condition means are the same)

Question 7

What does a graph look like when: you are looking at main effect of Factor A

Question 8

What does a graph look like when: you are looking at main effect of Factor B

Question 9

What does a graph look like when: Cross-over interaction between Factor A and B

Question 10

What does a graph look like when: Facilitatory interaction between Factors A and B

Question 11

What does a graph look like when: Main effect of Factors A and B, but no interaction