Discovering Statistics; Chapter 11 Flashcards
What is the most grand variance?
The variance of all observations.
What does MSm represent?
The average amount of variation explained by the model.
What does MSr represent?
The average amount of variance explained by extraneous variables.
How do we test the assumption of homogeneity of variance with ANOVA?
Levene’s test; conducted on the absolute differences between the observed scores and the mean/median of the group from which each score came.
If significant (ie. p = .05) = assumption violated.
What are the two corrected versions of the F-Ratio?
Brown-Forsythe F and Welch’s F (computed in SPSS).
Can the F statistic be robust?
When all group sizes are equal, it can be robust to violations of normality.
What is a planned contrast?
Used when you have specific hypothesis to test, to compare b coefficients.
What is post-hot testing?
Used when you don’t have a specific hypothesis to test, to compare b coefficients.
What are the different types of planned contrast?
1) Devation; first; compares each category (exc. 1st) to overall experimental effect; last; same but exc. last.
2) Simple; first; each category compared to 1st category; last; same but compared to last.
3) Repeated; each category compared to prev. category
4) Helmert; each catgeroy compared every subsequent category
5) Difference; each category compared to every previous category.
What is polynomial contrast?
Tests for trends in the data; most basic for is the linear trend (no change in direction), but also have quadratic (1 change), cubic (2 changes) and quartic (3 changes).
What are post-hoc tests?
Pairwise comparisons designed to compare all different combinations of treatment groups.
Are post-hoc tests robust?
No, they perform badly under varying group sizes and population variables.
In ANOVA testing, what is the R2 value usually referred to as?
Eta squared (n2)
How do we report ANOVA?
F(DFm, DFr) = F value, p = ‘sig.’ value.
