[Eeglablist] Double Dipping with ICA

[Makoto Miyakoshi]

Dear Nick,

Two things.

1. The second ICA you mentioned does not change the result. Just try it and
you see what happens.

2. Double dipping refers to a procedure that is known to inflate Type I
error. ICA uses mutual information, and you test amplitude/phase
metric--these two do not have apparent correlation. If you say, cluster ICs
by ERP waveforms, then perform ERP amplitude difference, this is double
dipping (why? because IC cluster's ERP variance is minimized by clustering,
but this variance information is being used in the subsequent statistical
test)

Given that,

> Are there reasons not to do this or to do it?

You may do so but it is meaningless because the second ICA in that case
does nothing. And this has nothing to do with the double dipping problem.

Makoto

On Sun, Nov 8, 2020 at 8:22 AM Nicholas Dogris <
drdogris at neurofieldneurotherapy.com> wrote:

> Will my data be distorted if I run ICA, remove IC's such as eye blinks, and
> then run ICA again on the same dataset?  Are there reasons not to do this
> or to do it?
>
> Cheers,
>
> Nick
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