Which value is my within-participants degrees of freedom (df2) in my anovan (mixed anova) table?

Hello,

I have performed a mixed anova using anovan, where Roi, Localiser, Inversion and Eccentricity are within-subjects fixed factors and Participant is my between-subjects random factor. I am trying to report these results in APA format. It's obvious which value is my df1, but which is df2? This is not clear to me.

Is it the error term? So e.g. Roi would be reported with (2, 2276)?

Or is it the df of the 3-way interaction with the within-subjects factor, so Roi would be reported with (2, 360)?

Any help appreciated!

Thanks,

Annie

Answer 1

[Sai Pavan]

Hi Annie,

I understand that you want to know the within-subjects degrees of freedom (df2) value to report the results in APA format.

For a mixed ANOVA with within-subjects, "df1” typically represents the degrees of freedom associated with the effect of interest, while "df2” represents the error degrees of freedom, which are associated with the residual variation in the model. The "df2” value is typically obtained from the error term in the ANOVA table. It represents the total number of observations minus the total number of parameters estimated in the model.

If you are reporting the results for the Roi factor, it would be appropriate to report it as (2, 2276), where df1 = 2 is the degrees of freedom associated with the Roi factor, and df2 = 2276 is the error degrees of freedom in the ANOVA table.

Please refer to the below article to learn more about degrees of freedom in statistical tests: https://medium.com/@rondotsch/degrees-of-freedom-tutorial-8d8e5c7be6ec

Hope it helps.

Regards,

Sai Pavan