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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