wk8 Flashcards
One way between subjects ANOVA
an extension of an independent T test
three or more different groups of participants
One way within subjects ANOVA
extension of a within subjects t test
same group of participants tested in three or more conditions
assumptions for a ANOVA
1) equal numbers of participants in each group
2) normally distributed data
3) homogeneity of variance across the conditions
4) Data should be either interval or ratio
to calculate the F value
1) calculate sum of squares
2) calculate the three degrees of freedom
3) Calculate the mean sum of squares
4) calculate the F value
Sum of squares
measures how far individual measurements are from the mean.
subtract each measurement from the mean/ square the difference /and add up all resulting measurements
SS total
how much the scores vary in general from the grand mean
SS between
how much the group means varied
SS error (between)
How much participants varied from these group means
df
df between = number of conditions - 1
df total = N-1
df error = df total - df between
mean sum of squares (MS)
MS between = SS between/ df between
MS error = SS error / df error
F value
ME between / MS error
Post-hoc tests
we need this when we have a significant effect with a ANOVA and more than three groups or conditions
when to use post hoc tests
significant result
Tukey’s post hoc test for between subjects designs
tells you which conditions differ to which.
Sphericity assumption
homogeneity of variances of the differences between conditions
