Artefact detection - zsum implementation question

Danny Oude Bos d.oudebos at GMAIL.COM
Thu Oct 11 09:55:08 CEST 2007


At the moment I'm working with the artefact detection functions from
Fieldtrip. I think using z-values is very smart, but I do have a question
about the implementation.

The z-values are calculated per time sample per channel, and then summed
over the channels. But to do this, should you not take the absolute values
of the z-values?

A z-value can be positive or negative depending on a positive or negative
deviation from the average. For artefact detection however only the fact
that there is a deviation is important, not whether it is positive or
negative. Also, summing large positive and large negative deviations could
result in a low zsum, while there is most definitely something going on.

Thank you for your time.

Kind regards,

Danny Oude Bos.

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