[FieldTrip] Regression of behavioral data against EEG data

[Ivaylo Iotchev]

Interpreting and averaging p-values is not the same thing. P-values answer
a very specific question and are the last step of any inquiry, all
averaging, separation, other combinations of data happen before a p-value
is calculated.

Am Mo., 12. Dez. 2022 um 11:35 Uhr schrieb Burcu Bayram via fieldtrip <
fieldtrip at science.ru.nl>:

>
> Thank you very much for your reply!
>
> Would you be so kind to elaborate on why interpreting or averaging
> r-squared values or p-values does not make much sense?  And why
> r-squared values give a very reasonable topography, but one that is so
> much different from the topography of beta values?
>
> Best regards,
> Burcu
>
> On 12.12.2022 08:18, Schoffelen, J.M. (Jan Mathijs) via fieldtrip wrote:
> > Hi Burcu,
> >
> > Conventially, the parameter estimates (i.e. the beta weights) are
> > taken to the second level for an inferential statistical test.
> > Averaging p-values, or r-squared values is usually not done, and also
> > does not make much sense.
> >
> > Best wishes,
> > Jan-Mathijs
> >
> >
> >> On 10 Dec 2022, at 17:07, Burcu Bayram via fieldtrip
> >> <fieldtrip at science.ru.nl> wrote:
> >>
> >> Dear FieldTrip community,
> >>
> >> I'm new to regression analysis of EEG data and unsure which regression
> >> outputs to use. Beta-coefficients give a very different pattern of
> >> results compared to r squared values or p-values, although all of them
> >> (to my understanding) should express a form of relation between the
> >> two datasets. We are looking for help regarding the interpretation of
> >> those data and which one to select for our analysis. In our model,
> >> behaviour is the predictor and EEG activity is the outcome. The
> >> datapoints for each are single experimental trials (~2000 per
> >> subject).
> >> So far, we just used simple linear regression, but the plan is to use
> >> multiple linear regression at a later stage.
> >> The idea is to plot and interpret the regression results as if they
> >> were EEG amplitudes. So we get a time course and a topography of
> >> regression results, that help us to determine where and when in the
> >> brain behavior predicts neural activity. Our main questions are:
> >>
> >> 1. Which value makes most sense to use as an indication of brain/
> >> behavior relationship? The betas should provide the quality/ direction
> >> of the relationship, but don't say anything about how large or
> >> important that relationship is. The r squared or also the t or p
> >> values for each coefficient tell something about the strength of the
> >> relationship. The issue is, that they give really different activity
> >> patterns. You can see the topographies of beta values, r squared
> >> values and p-values in the attached images.
> >>
> >> 2. The second question is which of the single-subject regression
> >> outputs actually can be used for group level plots and statistics: Is
> >> it possible to average over e.g. betas or p-vales across subjects, and
> >> also do group level statistics with (e.g. compare group-level p-values
> >> or betas between two conditions)?
> >>
> >> Thank you so much in advance!
> >>
> >> Best regards,
> >> Burcu
> >>
> <beta_av_postmean.png><p_values_av_postmean.png><r_squared_av_postmean.png>_______________________________________________
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> >>
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> >
> >
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