Wrong error term for test of random factor in two-way mixed-effects ANOVA in SPSS

[bsbk]

In SPSS 21 on Mac OS 10.9.5, when I run a two-way mixed-effects ANOVA (with factor A fixed and factor B random), the between subjects effects table reported by SPSS uses mean square for the interaction (MS_AB) as the error term for testing the main effect of factor B, the random factor. According to Keppel and Wickens (2004) and Maxwell and Delaney (2004, p. 477) the error term for the main effect of factor B, the random factor, should be MS_within.

While it is easy to grab the correct error term and manually compute the F and p values, the reporting of the wrong F and p values for the random factor is misleading and could throw off a less-than-careful analyst.

Am I missing something or is this an error in SPSS's reporting?

[Bruce Weaver]

Perhaps this will help:

  http://www.angelfire.com/wv/bwhomedir/spss/SPSS_GLM_mixed_model.html

I apologize for the pop-ups that are likely to happen on Angelfire.  One day, I may get around to moving that to my more current Google Sites pages.  

bsbk wrote

In SPSS 21 on Mac OS 10.9.5, when I run a two-way mixed-effects ANOVA (with factor A fixed and factor B random), the between subjects effects table reported by SPSS uses mean square for the interaction (MS_AB) as the error term for testing the main effect of factor B, the random factor. According to Keppel and Wickens (2004) and Maxwell and Delaney (2004, p. 477) the error term for the main effect of factor B, the random factor, should be MS_within.

While it is easy to grab the correct error term and manually compute the F and p values, the reporting of the wrong F and p values for the random factor is misleading and could throw off a less-than-careful analyst.

Am I missing something or is this an error in SPSS's reporting?

[bsbk]

That answers my question, thanks.

On Fri, Dec 5, 2014 at 2:37 PM, Bruce Weaver [via SPSSX Discussion] <[hidden email]> wrote:

Perhaps this will help:

  http://www.angelfire.com/wv/bwhomedir/spss/SPSS_GLM_mixed_model.html

I apologize for the pop-ups that are likely to happen on Angelfire.  One day, I may get around to moving that to my more current Google Sites pages.  

bsbk wrote

In SPSS 21 on Mac OS 10.9.5, when I run a two-way mixed-effects ANOVA (with factor A fixed and factor B random), the between subjects effects table reported by SPSS uses mean square for the interaction (MS_AB) as the error term for testing the main effect of factor B, the random factor. According to Keppel and Wickens (2004) and Maxwell and Delaney (2004, p. 477) the error term for the main effect of factor B, the random factor, should be MS_within.

While it is easy to grab the correct error term and manually compute the F and p values, the reporting of the wrong F and p values for the random factor is misleading and could throw off a less-than-careful analyst.

Am I missing something or is this an error in SPSS's reporting?

--
Bruce Weaver
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