12. Comparison of Several Means 4 Flashcards
When are repeated measures designs used?
- same people exposed to different types of treatment
- same people exposed to one treatment and measured over time
What are repeated measures assessing (differences)?
within-group, NOT between group
assumptions of repeated measures
- normally distributed data
- DV measured at interval level
- sphericity
sphericity
similar to homogeneity of variance in a between group ANOVA
For sphericity to be an issue, what must be present?
need 3 conditions (ex. 3 different treatments, 3 different time periods)
What is sphericity measured by?
Mauchly’s test
Mauchly’s test = greater than 0.05
- significant
- assumption has been met
Mauchly’s test = less than 0.05
- not significant
- assumption has been violated
What happens if sphericity is violated?
can apply corrections
What are the corrections to apply if sphericity is violated?
- Greenhouse-Geisser correction
- Huynh Feldt correction
- Bonferroni correction
used if Mauchly’s test is less than 0.75
Greenhouse-Geisser correction
used if Mauchly’s test is more than 0.75
Huynh Feldt correction
Which is the best post hoc test to used if sphericity is violated?
Bonferroni correction
f-stat for repeated measures: experiment effect
effect of the experiment shows up as within group variance vs between group
for repeated measures f-stat, within-group variance is split into __ groups
2
For repeated measures f-stat, what groups are within group variance split into?
- variance explained by the experiment
- unexplained variance - error
What is a mixed design ANOVA?
- mixture of between group and within group variables
between group variables
1 way ANOVA
within group variables
repeated measures
for a mixed design ANOVA, what must you have
at least 2 IVs
- 1 must include different participants (between group)
- 1 must include same participants (within group)
Assumptions of a mixed design ANOVA
- normality of data
- DV at interval level
- independence (between group IV only)
- homogeneity of variance (between group IV only)
- sphericity (within group IV only if more than 3 conditions or time periods)
f-stat for mixed design ANOVA
model sum of squares
broken down into within group and between group variance
