# [Eeglablist] Trial-by-trial median absolute deviation (MAD) of amplitude and latency

Stephen Politzer-Ahles politzerahless at gmail.com
Tue May 2 14:39:03 PDT 2017

```EEG.data is a channels*samples*trials structure for one participant. So,
for example, this would give you the amplitude at channel 5 and timepoint
100 for each trial:

EEG.data(5,100,:)

MATLAB has a built-in mad() function, although anyway median absolute
deviation is basic arithmetic so it shouldn't be hard to calculate.

This would give you the median absolute deviation of the amplitude at each
timepoint; to get median absolute deviation of P1 amplitude and latency,
you would just have to first calculate the P1 amplitude and latency at each
trial and each channel, and then get the mad() of those values.

---
Stephen Politzer-Ahles
The Hong Kong Polytechnic University
Department of Chinese and Bilingual Studies
http://www.mypolyuweb.hk/~sjpolit/
<http://www.nyu.edu/projects/politzer-ahles/>

On Tue, May 2, 2017 at 1:21 PM, Morett, Laura <laura.morett at yale.edu> wrote:

> Dear colleagues,
>
> In order to obtain a measure of inter-trial variability within subjects, I
> would like to compute trial-by-trial median absolute deviation (MAD) of
> amplitude and latency within epochs.  Given that two published papers have
> used EEGLab to do this (citations below), I know it is possible to at least
> output data in a format that will allow computation of this measure, if not
> to compute it directly in EEGLab.  However, I am unsure of which
> function(s) to use to do this.  Any guidance anyone can provide would be
> greatly appreciated.
>
>
>
> Many thanks,
>
> Laura Morett
>
>
>
>
>
> Arazi, A., Censor, N., & Dinstein, I. (2017). Neural variability quenching
> predicts individual perceptual abilities. *Journal of Neuroscience*, *37*,
> 97-109.
>
>
>
> Milne, E. (2011). Increased intra-participant variability in children with
> autistic spectrum disorders: evidence from single-trial analysis of evoked
> EEG. *Frontiers in psychology*, *2*, 51.
>
>
>
>
>
> ********************************************************
>
> Laura M. Morett
>
> Hilibrand Postdoctoral Fellow
>
> Yale Child Study Center
>
> 230 S. Frontage Rd.
>
> New Haven, CT 06520
>
>
>
> As of August 16, 2017:
>
> Assistant Professor of Educational Psychology
>
> Educational Neuroscience Initiative
>
> University of Alabama
>
> Box 870231
>
> Tuscaloosa, AL 35487-0231
>
>
>
> Email: laura.morett at yale.edu
>
> Phone: (203) 737-4586
>
> Web: http://lauramorett.strikingly.com/
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__lauramorett.strikingly.com_&d=CwMF-g&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=7RydtjFxlOLitiTKeuyufwjZVnuS2cr0LD3ZBHQd6QA&m=hcKHc9qk081CzOBRcCJRuXs-41-8mLMuX9gmiw_QG_g&s=UQlF7t1IaNyCaJW5l4lvUXFZvEYnMtD2_GIYvnLLIaE&e=>
>
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