non-parametric cluster analysis

[Emanuel van den Broeke]

Dear dr. Maris,
I would like to ask a question regarding your article: Nonparametric statistical 
testing of EEG- and MEG-data in Journal of Neuroscience Methods 2007. I 
hope you will answer it.
My question is about the following. I want to use the non-parametric cluster 
analysis, the one you described in your article, for my ERP analysis. 
In this article you quantified the difference between the two conditions 
(congruent and incongruent) by calculating sample specific t-values, based on 
the t-distribution. These sample specific t-values were calculated based on a 
two sided test statistic and an alpha of .05. Subsequently clusters were 
chosen based on the uncorrected critical t-value. This uncorrected critical t-
value is also based on a two sided test statistic. 
Now my question. I understand that this uncorrected critical t-value threshold 
affects the sensitivity of the statistical test rather than the validity. So is it 
also possible to calculate the sample specific t-values belonging to the one-
sided test statistic, instead of two-sided? The same question accounts for the 
uncorrected critical t-value used as threshold.
Thanks in advance,
Best,
Emanuel

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