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 was a 9x9 Within Subject Incomplete Counterbalanced Measures Design
The data was collected to measure the effect of common distortions across multiple websites.
Mauchly's Test of Sphericity Measure: MEASURE_1 Within Subjects | Mauchly's W| Approx. | df | Sig.| Epsilon Effect | | | | |---------------------------- | | Chi-Square | | |Greenhouse-| Huynh-| Lower | | | | |Geisser | Feldt | bound website | .024| 41.546| 35 | .247| .579| .900| .125 distortions | .111| 24.430| 35 | .925| .655| 1.000| .125 | | | | | | | website * | | | | | | | distortions | .000| . | 2079 | . | .180| 1.000| .016
I understand from this question/answer and this question/answer that this might happen when there are only 2 factors with 2 levels but in my case there are 2 factors (website, distortion) each with 9 levels. Each of these levels has 15 data observations.
Alternatively I also note from this Laerd Statistics guide "the greater the number of repeated measures, the greater the potential for the violation of sphericity". Maybe 9x9 is too much and/or the value is uncomputable?
I understand that if Mauchly's Test returns a Sig value <.05 I should turn to the Greenhouse-Geisser and Huynh-Feldt values and that the lower these values are the greater the violations of sphericity. However, the Huynh-Feldt value of 1 indicates perfect sphericity while my Greenhouse-Geisser is .180 indicating there is an issue.
Has anybody else experienced this problem? And what does it mean? Am I to assume that there is an issue with Sphericity? Which correction should I use?
So after some investigation it looks like the test is simply too complicated, possibly for my machine.
When I did the same test with a small sample of the same data, a 3x3 design each with 6 data observations the test worked. Both the Approx. Chi-Square value and the Sig value were visible.
4x4 with 12 data observations also works
However, when I did it with a more complex 5x5 design, each with 15 data observations it would no longer give me either value.
EDIT 2: Not Memory
To increase the memory allocations to SPSS simply:
- Open a new Syntax window. File > Open > Syntax.
SHOW WORKSPACEand click run to show the current memory allocation
- This was 24576 in my case (memory shown in KB)
- To increase your memory type
SET WORKSPACE= 49150and click run
- Note: I read somewhere that it should be increased by X2 each time
I increased this all the way to 3145600 kb (yup 3.14 GB) and it still did not work so it must not be a memory issue.