Week 7 Flashcards
(19 cards)
What is a one-way repeated measures ANOVA
The one way repeated measures ANOVA is used in research situations where the same people contribute to all means, all the same people are in all experimental conditions
The repeated-measures ANOVA controls for individual differences
How is variance partitioned inside SS Within
SS Subject (Variance within subjects)
SS Error (Unexplained variance)
What is SS Total
The Total variance between each score and the grand mean
What is SS Between
The variance in each groups mean to the grand mean
What is SS Within
The difference from each data point to the group mean (within group variance)
What is SS subject
The difference between each point and the grand mean
What is SS Error
It is the remaining amount of variance (error variance)
Calculated with:
SS Within - SS Subject
What is mean squares used for.
Calculated to eliminate the bias associated with the number of scores used to calculate SS
How is the F-ratio calculated
MS Between / MS Error
What is sphericity
Sphericity assumes that the relationship between pairs of experimental conditions is similar, or, that the level of dependence between experimental conditions is roughly equal.
Explain compound symmetry
Sphericity falls under the banner of compound symmetry.
Compound symmetry occurs when both the variances across conditions are equal, and when the covariances between pairs of conditions are equal.
What does compound symmetry assume
It assumes that the variation within the experimental conditions is fairly similar and that no 2 conditions are any more dependent or related than any other 2.
When the test statistic is significant has the assumption of Mauchly’s test been violated
Yes
When the test statistic is not significant has the assumption of Mauchly’s test been violated?
No
What is Mauchly’s Test affected by
Sample size.
Very big samples = only small deviations from sphericity can produce a significant test statistic.
Very small samples = sometimes even quite large deviations from sphericity can produce a non-significant test statistic.
What happens when the assumption of sphericity has been violated
Then there is a significant loss in the power of the F-test and inaccuracies in the F-ratio that is produced in the output.
If data violated the sphericity assumption what do we use
Greenhouse-Geisser Correction or Huynh-Feldt Correction
Explain Greenhouse-Geisser Correction
Varies between 1/(k-1) and 1 (where k is the number of repeated-measures conditions)
The closer the correction is to 1, the more homogeneous the variances of differences and the closer the data are to being spherical
This correction can be over conservative
Explain the Huynh-Feldt Correction
Is a less conservative correction than the Greenhouse-Geisser correction
But it can overestimate sphericity
