mne.stats.permutation_t_test¶

mne.stats.permutation_t_test(X, n_permutations=10000, tail=0, n_jobs=1, seed=None, verbose=None)[source]¶

One sample/paired sample permutation test based on a t-statistic.

This function can perform the test on one variable or simultaneously on multiple variables. When applying the test to multiple variables, the “tmax” method is used for adjusting the p-values of each variable for multiple comparisons. Like Bonferroni correction, this method adjusts p-values in a way that controls the family-wise error rate. However, the permutation method will be more powerful than Bonferroni correction when different variables in the test are correlated (see [1]).

Parameters

Xarray, shape (n_samples, n_tests): Samples (observations) by number of tests (variables).
n_permutationsint | ‘all’: Number of permutations. If n_permutations is ‘all’ all possible permutations are tested. It’s the exact test, that can be untractable when the number of samples is big (e.g. > 20). If n_permutations >= 2**n_samples then the exact test is performed.
tail-1 or 0 or 1 (default = 0): If tail is 1, the alternative hypothesis is that the mean of the data is greater than 0 (upper tailed test). If tail is 0, the alternative hypothesis is that the mean of the data is different than 0 (two tailed test). If tail is -1, the alternative hypothesis is that the mean of the data is less than 0 (lower tailed test).
n_jobsint: The number of jobs to run in parallel (default 1). Requires the joblib package.
seedNone | int | instance of RandomState: If seed is an int, it will be used as a seed for RandomState. If None, the seed will be obtained from the operating system (see RandomState for details). Default is None.
verbosebool, str, int, or None: If not None, override default verbose level (see mne.verbose() and Logging documentation for more). If used, it should be passed as a keyword-argument only.

Returns

T_obsarray of shape [n_tests]: T-statistic observed for all variables.
p_valuesarray of shape [n_tests]: P-values for all the tests (a.k.a. variables).
H0array of shape [n_permutations]: T-statistic obtained by permutations and t-max trick for multiple comparison.

Notes

If n_permutations >= 2 ** (n_samples - (tail == 0)), n_permutations and seed will be ignored since an exact test (full permutation test) will be performed.

References

1: Nichols, T. E. & Holmes, A. P. (2002). Nonparametric permutation tests for functional neuroimaging: a primer with examples. Human Brain Mapping, 15, 1-25.