analysis of covariance lec 7 Flashcards
what does ANCOVA stand for
analysis of covariance
what happens if we reduce error variance
higher f value, more significant
if we measure the sources of error variance we can…
take them out of the equation
some variation could also be due to…
error caused by nuisance variables
what does removing nuisance variables do
reduces error variance increasing the f value and increasing statistical power
what is a covariate
the error variance, such as vocabulary for spelling test and teaching
what does an ancova do
split into three parts, covariate, ms between, error
ancova does what
adjusts the means estimating what they would be if the score for the covariate was the same for everyone
how to write up ancova analysis
design, factors and dvs
acova result
bonferroni correction
what assumptions should ancova meet
covariate and the factor should be independent
the relationship between the covarite and DV is linear
homogeneity of regression slopes
what does covariate and the factor being independant mean?
should be independent, such as sex and age, not salary and gender
what does the relationship between the covariate and DV being linear mean
a linear relationship, straight up
what does homogentiy of regression slopes mean
assume the relationships between the covariate and the DV. is roughly the same in each condition eg all going straight up in plotw
what is the homogentiy of regression slopes is not parallel
suggests an interaction between the IV and the covariate, which if significant should use blocking rather than ANCOVA. if non significant, can use ANCOVA
