Sphericity is an assumption of repeated measures ANOVA. It states that the variance of all pairwise differences is constant.
Sphericity is an assumption of repeated measures ANOVA. It states that the variance of all pairwise differences is constant.
Questions tagged [sphericity]
46 questions
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Differences between MANOVA and Repeated Measures ANOVA?
What is the difference between a repeated measures ANOVA over some factor (say experimental condition) and a MANOVA?
In particular one website I stumbled across suggested that MANOVA does not make the same assumption of sphericity that repeated…
russellpierce
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Post-hocs for within subjects tests?
What is the preferred method for for conducting post-hocs for within subjects tests? I've seen published work where Tukey's HSD is employed but a review of Keppel and Maxwell & Delaney suggests that the likely violation of sphericity in these…
russellpierce
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Why does repeated measures ANOVA assume sphericity?
Why does repeated measures ANOVA assume sphericity?
By sphericity I mean the assumption that the variance of all pairwise differences between groups should be the same.
In particular, I don't understand why this should be the assumption and not that…
user1205901 - Reinstate Monica
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Does Greenhouse-Geisser correction influence the effect size estimation, the statistical significance treshold, or both of them?
I discussed recently with one of my colleagues about the Greenhouse-Geisser correction for non-sphericity. I told him first that this correction is very conservative and that it would be more efficient to perform an alternative analysis not relying…
Psychokwak
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How to get Sphericity in R for a nested within subject design?
Thank you for reading. I am trying to get sphericity values for a purely within subject design. I have been unable to use ezANOVA, or Anova(). Anova works if I add a between subject factor, but I have been unable to get sphericity for a purely…
Adam SA
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Reproducing this chi-square probability from published work
So i'm working on a Greenhouse-Geisser correction and i found this "John, Nagao & Sugiura’s test for sphericity" in this publication (https://www.utdallas.edu/~herve/abdi-GreenhouseGeisser2010-pretty.pdf).
Could it be that they calculated the value…
T.Tos
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Bonferroni and Greenhouse-Geisser corrections with repeated-measures ANOVA
I guess my question comes in two parts:
Following a 1x7 repeated-measures ANOVA, I carried out 3 pre-planned tests. Two were t-tests between 2 of the conditions. The third is a 1x6 ANOVA (to test significance between conditions 2-7). My question…
Eric
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Issues with the Huynh-Feldt values using either Anova or ezANOVA in R?
Is there an issue with the output of the Huynh-Feldt correction when running an ANOVA for both between and within factors (mixed design) in R? My issue is that when I run a 'within-subject (only)' ANOVA using either the 'Anova' or 'ezANOVA'…
Sean Estrada
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Why is compound symmetry sufficient to establish sphericity?
At this website it is stated that "If compound symmetry is met then sphericity is also met."
Is it impossible to construct a data set that has perfect compound symmetry but not perfect sphericity? Why/why not? It's not intuitively obvious to me…
user1205901 - Reinstate Monica
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4
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What is the origin of the Winer's compound symmetry test of the variance-covariance matrix?
In his famous book, Winer (Statistical principles in experimental design 1971; reedited Winer, Brown, Michels, 1991, p. 517) introduced a test of compound symmetry. The test expands on the likelihood ratio test of Wilks (1934) with a correction…
Denis Cousineau
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Box's test for equal covariances or Mauchly's test of sphericity?
I am writing a report on a 2 x 3 mixed study. There is ONE within IV with TWO levels and there is ONE between subjects IV THREE levels. There are two DVs.
Sample sizes for each group is 25, 25, 27.
I tried Mauchly's test but it does not produce any…
buket dogan
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estimating sphericity
I have $n$ independent samples from a $p$-dimensional multivariate normal distribution with mean 0 and covariance $\Sigma$. Optimally, the $p$ variables should uncorrelated and of equal variance ($\Sigma = \sigma^2 I_p$; white, spherical), and I…
A. Donda
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Why is ezANOVA not giving me Mauchly´s test of sphericity, even though I belive I have more than 2 levels of within-Ss variables?
I am trying to do learn how to do a repeated measure in R using ezANOVA and I have used the following command:
> ezANOVA(data=NL2, dv=.(ln.conc.), wid=.(sample), within=.(time),
> between=.(pH), type=1, detailed=TRUE)
This is my output and my…
Marja
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No value or "."returned for Mauchly's Test of Sphericity in SPSS
I am learning how to do a Two-Way Repeated Measures ANOVA in SPSS but when I try to check the Mauchly's Test of Sphericity Significance value it only displays a single decimal point. It is also missing the Approx. Chi-Square value.
The experiment…
Deepend
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Why is the "sphericity assumption" in RM-ANOVA (constant variance of difference scores) called "sphericity"?
Why is the "sphericity assumption" in RM-ANOVA, i.e. the assumption of constant variance of difference scores, called "sphericity"?
(This question was suggested in the comments to a related question.)
The term seems more suited to describe compound…
user1205901 - Reinstate Monica
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