12. Comparison of Several Means 3 Flashcards
When is an ANCOVA used?
when researchers have identified continuous variables that may influence the DV but aren’t one of the IVs
What is the variable in an ANCOVA called?
covariate
2 reasons to use an ANCOVA
- reduce within group error variance
- elimination of confounds
what does reducing within group error variance accomplish?
allows researchers to explain some unsystematic variance in terms of the covariate
Elimination of confounds: when can this be accomplished?
ANCOVA removes bias of these variables if they are known apriori and measurable
types of factorial design
- independent factorial design
- repeated measures factorial design
- mixed design
factorial design: independent factorial design
- 2+ IVs measured using different participants
- between group differences
factorial design: repeated measures factorial design
- 2+ IVs that have been measured on the same participants
- within group differences only
factorial design: mixed design
2+ IVs that have been measured with
- at least 1 measured on the same participants AND
- at least 1 measured on different participants
mixed design has these types of differences
- between group
- within group
2-way ANOVA: how many IVs?
2
2-way ANOVA: what type of design?
independent factorial design
2-way ANOVA: example
3+ groups, each broken down by gender
- 1 IV is the group
- 1 IV is gender
How is SS_T broken down?
into variance explained by the experiment (SS_M) and unexplained variance (SS_R)
How is model sum of squares broken down?
- variance explained by the first IV
- variance explained by the second IV
- variance explained by the interaction of the first and second IV
