ANOVA Flashcards
You could do 3 t-tests but that would…
Increase the likelihood of type 1 errors: finding significance when there is none
ANOVA used for…
Comparing groups or conditions
>2 groups = ANOVA (t-test 2 groups)
Parametric…
ANOVA
Almost always used, very robust
Non-parametric…
Kruskal-Wallis Test
Letter representing ANOVA
F
F-ratio represents…
Variance between groups / variance within groups
A significant F values means that we can…
Reject the null hypothesis
But it does not tell us which groups differ…
A post-hoc test…
Similar to a t-test
Correction for family-wise alpha errors built into them
Two most commonly used post hoc tests…
Scheffe’s confidence interval
Tukey’s honestly significance difference (HSD)
One-way ANOVA, what do you need?
One independent variable with three or more levels
One continuous dependant variable
ANOVA output…
F values
Multiple comparisons box
Repeated measures ANOVA, when do we need this?
One group
One dependant variable
3 or more time periods
Sphericity is…
An assumption of repeated measures ANOVA, replacing homogeneity of variance
If sphericity is violated…
We use a correct statistic: epsilon
Sphericity perfect= 1
Sphericity tests….
Mauchly’s test of sphericity- if answer yes we use epsilon to adjust degrees of freedom
Greenhouse-Geisser
Huynh-Feldt
Wilks’ Lambda- when sample sizes equal and observations independant
