Hello all,
I know there is a very similar question with several pages of answers in Reserach Gate, but the post was created quite a while ago, so I just want to start a new discussion about the Mauchly's Test of Sphericity.
I am using a repeated measures ANOVA. The data contain 2 groups (16 patients and 10 health controls) and 11 repeated measurements. For some reason, the SPSS returned just a dot for ChiSq and Sig. Also, Mauchly's W = 0 and Epsilons were .500 (Greehouse), .522 (Huynh), and .500 (Lower-bound).
I currently don't know why this occurs. Any opinions or suggestions to try out?
Thank you!
Hi,
Kindly check the variable property in the variable list. Handling SPSS needs these minor checks. And why would you be doing ANOVA (which is for a continuous variable) and a chi square (which is for categorical variable) together . Mauchly's test is purely to validate the repeated ANOVA test.
More information is required.
Sometimes, this result maybe comes from your dataset. I think you can find more details about other ANOVA exercise case (for example Youtube ) and the way of making discussion about the Mauchly's Test of sphericity. Anyway, it is just a test value, I think it cannot completely be used to judge this ANOVA is right, so you just need to find your analysis is reliable.
Hello Sanghee,
The N = 16 should be sufficient, even with 11 measurements, for a one-between (your two groups), one-within (11 measurements) subjects design to yield the three usual tests as well as a check of sphericity. My guess is that you're either using a different statistical design than what I've assumed or there's something unique about your data set (as Kai Liu suggested)...maybe the correlations among the 11 measures are very high, for example, suggesting redundancy.
SPSS does 'fail' to run the Mauchly test if the trace [sum of the values on the main diagonal] of the r x r matrix* of residual sums of squares and cross-products (r = number of non-redundant measures), is less than or equal to zero (according to SPSS documentation; pp. 515-516 of ftp://public.dhe.ibm.com/software/analytics/spss/documentation/statistics/24.0/en/client/Manuals/IBM_SPSS_Statistics_Algorithms.pdf).
So, do check the correlations among the measures for your data.
Good luck with your work!
* I simplified this slightly; the matrix is pre-multiplied and post-multiplied by a function of the polynomial contrast matrix for the repeated measures factor.
Thanks everyone. I think it was caused by the dataset. The correlations among 11 measures look pretty high! wow! Thanks a lot.
Adding to the question -- I've had the same conflict with SPSS not providing a p-values for Mauchly's Test of Sphericity; this occurred for two different 3-WAY-RM-ANOVAs I recently ran.
In one of the 3-WAY-RM-ANOVAs I have a total of 89 subjects; I have 1 within-subject repeated measure (with 75 levels); I have 2 between subject factors (one with 2 levels and one with 6 levels). I attached screenshots of the data- and variable views for this ANOVA; no p-value was provided for Mauchly's Test of Sphericity.
In the second 3-WAY-RM-ANOVA, I have a total of 14 subjects; I have 1 within-subject repeated measure (with 75 levels); I have 2 between subject factors (each between subject factor has 2 levels).
Can anyone provide any suggestions?
IMO, the SPSSX-L forum is a much better place to post questions of this nature. Members of that discussion forum include current and former employees of IBM-SPSS. One way to join is to visit the Nabble archive (link below) and click the "more options" link at the top of the page. HTH.
- http://spssx-discussion.1045642.n5.nabble.com/
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