rlying the second
      sample.
    * 'greater': the mean of the distribution underlying the first
      sample is greater than the mean of the distribution underlying
      the second sample.

    .. versionadded:: 1.7.0

Returns
-------
statistic : float or array
    t-statistic
pvalue : float or array
    two-tailed p-value

Notes
-----
For more details on `ttest_rel`, see `scipy.stats.ttest_rel`.

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