Statistics¶

Models¶

• mne.stats.linear_regression() allows to compute ordinary least square regressions on multiple targets, e.g., sensors, time points across trials (samples). For each regressor it returns the beta values, t-staistics, and uncorrected significance values. While it can be used as a test it is particularly useful to compute weighted averages.
• mne.stats.f_mway_rm() computes a generalized M-way repeated measures ANOVA for balancd designs. It returns mass-univariate F-statistics and p-valus. The associated helper function mne.stats.f_threshold_mway_rm() allows to determine the F-threshold at a given significance level and set of degrees of freedom. Note that this set of functions was previously called mne.stats.f_twoway_rm and mne.stats.f_threshold_twoway_rm, respectively, only supporting 2-way factorial designs.
• mne.stats.ttest_1samp_no_p() is an optimized version of the one sample t-test provided by scipy. It is used by default for contrast enhancement in mne.stats.permutation_cluster_1samp_test() and mne.stats.spatio_temporal_cluster_1samp_test().
• mne.stats.f_oneway() is an optimized version of the F-test for independent samples provided by scipy. It can be used in the context of non-paramteric permutation tests to compute various F-contrasts. It is used by default for contrast enhancement in mne.stats.spatio_temporal_cluster_test() and mne.stats.permutation_cluster_test().

Multiple comparisons¶

In MEG and EEG analyses typically involve multiple measurements (sensors, time points) for each sample. In a mass-univariate analysis fitting statistical models for each of these observations a multiple comparison problem occurs (MCPP). MNE-Python provides the following functions to control for multiple comparison:

• mne.stats.bonferroni_correction() returns a boolean mask of rejection decisions and the corrected p-values. The Bonferroni correction reflects the most conservative choice and corrects for the MCPP by multiplying the p-values by the number of observations
• mne.stats.fdr_correction() implements False discovery rate (FDR) and also returns a boolean mask of rejection decisions and the corrected p-values.

More flexible handling of the MCPP can be achieved by non-parametric statistics.

Permutation clustering¶

As MEG and EEG data are subject to considerable spatiotemporal correlation the assumption of independence between observations is hard to justify. As a consequence the MCPP is overestimated when employing paramteric mass-univariate statistics. A flexble alternative is given by non-parametric permutation clustering statistics which implement a spatiotemporal priors and typically allow for clusterwise inference. These tests can be applied over a wide range of situations inclduing single subject and group analyses in time, space and frequency. The only requirement is that the scientific hypothesis can be mapped onto an exchangeability null hypothesis in which two or more conditions can be compared and exchanged across permutations to generate an empirical distribution.

The clustering permutation API in MNE-Python is grouped according to different contrasts of interest and clustering connectivity prior, i.e., assumptions about the grouping and neighborhood of the observations.

• mne.stats.permutation_cluster_1samp_test() supports paired contrasts with spatial prior.
• mne.stats.permutation_cluster_test() supports F-contrasts with spatial prior.
• mne.stats.spatio_temporal_cluster_1samp_test() supports paired contrasts without spatial prior.
• mne.stats.spatio_temporal_cluster_test() supports F-contrasts without spatial prior.

Using the TFCE option observation- instead of cluster-wise hypothesis testing can be realized.