[FieldTrip] statistical reporting cluster based permutation

[Stephen Politzer-Ahles]

Hello Kaelasha,

There isn't really any one absolute right way to report these; my best
suggestion is to look in the literature for other papers in your area that
have reported cluster based stats, and see how they do it. In my experience
it's usually sufficient to report the p-value, polarity, and approximate
spatiotemporal distribution of an effect (e.g., "there was a significant
positive effect (p=.042) based on a cluster of fronto-central electrodes
lasting from x ms to y ms..."), as is done in this paper:
https://www.researchgate.net/publication/38112722_Reasoning_with_Exceptions_An_Event-related_Brain_Potentials_Study
.
I also find raster plots to be a nice way to visualize the spatiotemporal
extent of a cluster; see, e.g., this paper:
http://joshuakhartshorne.org/papers/HartshorneSnedekerLiemAzarKim.pdf

See also
http://www.fieldtriptoolbox.org/faq/how_not_to_interpret_results_from_a_cluster-based_permutation_test
for some suggestions about wording and interpretation of the effects.

Best,
Steve



---
Stephen Politzer-Ahles
University of Oxford
Language and Brain Lab, Faculty of Linguistics, Phonetics & Philology
http://users.ox.ac.uk/~cpgl0080/
Message: 1

> Date: Sun, 15 Nov 2015 01:07:30 +0000
> From: Kaelasha Tyler <ktyler at swin.edu.au>
> To: "fieldtrip at science.ru.nl" <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] statistical reporting cluster based permutation
>         tests
> Message-ID:
>         <FB8747C478C3AF489C8F5164C02011B9E48CAE50 at gsp-ex01.ds.swin.edu.au>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi all,
>
> I am writing up results for cluster based permutation tests that I ran on
> masked priming meg data.
>
> I have to admit I am not entirely sure the exact form for reporting the
> stats on these.
>
> For example, when comparing two conditions, with n=20,  I have one
> significant positive cluster over left frontal and parietal areas. The
> stats for this cluster read:
>
> prob: 0.0420
> clusterstat: 1.2443e+04
> stddev: 0.0063
> cirange: 0.0124
>
> Has anyone else completed and rerooted on results, having used cluster
> based permutation tests?
> Mean values don't seem to be appropriate here, so would it simply be the p
> value and standard deviation for the significant clusters that would be
> reported on?
>
> Thanks,
> K
>
> PhD Candidate
> Brain and Psychological Sciences Research Centre
> Swinburne University of Technology
> Melbourne
> Australia
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20151115/3b193bd3/attachment-0001.html>