What does it mean if sphericity assumption is violated?
The sphericity assumption is satisfied when the variance of the difference between scores for any two levels of a repeated measures factor is constant. The sphericity assumption is violated when the variance of the difference between scores for any two levels of a repeated measures factor is not constant.
What do you do if Mauchly’s test of sphericity is significant?
→ If Mauchly’s test is significant then we cannot trust the F-ratios produced by SPSS. Fortunately, if data violate the sphericity assumption there are several corrections that can be applied to produce a valid F-ratio. All of these corrections involve adjusting the degrees of freedom associated with the F-value.
How do I report a violation of sphericity?
Repeated Measures ANOVA – APA Style Reporting of the sphericity assumption, χ2(2) = 7.17, p = 0.028.” If sphericity is violated, report the Greenhouse-Geisser ε and which corrected results you’ll report: “Since sphericity is violated (ε = 0.840), Huyn-Feldt corrected results are reported.”
What is the consequence of violating the assumption of sphericity quizlet?
What is the effect of violating the assumption of sphericity? 1) The F-ratio that we use in these situations, sphericity creates a loss of power and a test statistic that doesn;t have the distribution it’s supposed to have.
What is the significance of sphericity?
Sphericity is a measure of the degree to which a particle approximates the shape of a sphere, and is independent of its size. Roundness is the measure of the sharpness of a particle’s edges and corners.
How do I report Mauchly’s test of sphericity?
Therefore, we could report the main finding as: → Mauchly’s test indicated that the assumption of sphericity had been violated, χ2(5) = 11.41, p = . 047, therefore degrees of freedom were corrected using Greenhouse-Geisser estimates of sphericity (ε = . 53).
What is the meaning of sphericity?
Sphericity is defined as the ratio of the surface area of a sphere to the surface area of the particle.
When repeated measures are used which assumption is violated?
Unfortunately, repeated measures ANOVAs are particularly susceptible to violating the assumption of sphericity, which causes the test to become too liberal (i.e., leads to an increase in the Type I error rate; that is, the likelihood of detecting a statistically significant result when there isn’t one).