ANOVA

Question 1

ANOVA

Answer 1

Used to compare the means of multiple groups on a single DV. However, this is a non-specific test and doesn’t explain where the differences lie.
ANOVA doesn’t consider patterns in data.

Question 2

ANOVA Test Statistic

Answer 2

F ratio is a comparison of model variance and error variance. If the ratio is greater than 1, there is an effect.

Question 3

Planned Contrasts

Answer 3

Method for breaking down how the groups in an ANOVA may differ. Theory driven and planned before conducting the analysis. Can also be used to assess patterns in data.

Question 4

Rules for Choosing Contrasts

Answer 4

Three Rules

1. Independence - shouldn’t use a separated group in more than one contrast.
2. Two chunks - only compare two groups at a time
3. K-1 - should always have one less contrast than number of groups.

Question 5

Rules for Coding Contrasts

Answer 5

1. Choose contrasts correctly
2. Groups with positive weight will be compared against groups with negative weights
3. Sum of weights = zero
4. Assign groups not involved with zero
5. Weights in one group should equal the number of groups in the other
6. Group coded lowest is first, group coded highest is last.

Question 6

Assumptions of ANOVA

Answer 6

Normality, no outliers, homogeneity of variance, linearity, independence.