ANCOVA Flashcards
Define a covariate.
Variable that cannot be controlled for in methodology but can be measured and accounted for in statistical analysis.
Define a covariate design.
Design in which a variable that correlates with the DV is measured and partialled out of analysis.
Define ANCOVA.
Main effects and interactions are assessed after DV scores are adjusted for differences associated with a covariate(s).
What is the first main purpose of ANCOVA?
Increase the sensitivity of F tests by reducing the error term.
How does ANCOVA reduce the error term?
Effects of the covariate are partialled out, making the covariate a control variable, therefore reducing unexplained.
What is the second main purpose of ANCOVA?
To adjust means on DV to what they would be if all participants scored equally on the CV.
Why is it useful to use adjusted means in ANCOVA?
When differences related to the CV are removed, the remaining differences are (hopefully) related to the effects of the IV.
What are the assumptions of ANCOVA?
DV and CV are continuous, IV is categorical, normality, independence of observations, homogeneity of regression slopes and homogeneity of error variance.
What is homogeneity of regression slopes?
When the relationship between the CV and the DV is the same for each group, as shown in regression lines in scatterplots and non-significant interaction of the CV and IV in ANOVA.
