code: def _parametric_ci(arr, ci=0.95):
      """Calculate the `ci`% parametric confidence interval for `arr`."""
      mean = arr.mean(0)
      if len(arr) < 2:  # can't compute standard error
          sigma = np.full_like(mean, np.nan)
          return mean, sigma
      sigma = stats.sem(arr, 0)
      return stats.t.interval(
          ci, loc=mean, scale=sigma, df=arr.shape[0]
      )
  
file_path: mne-python/mne/stats/parametric.py
imports: from functools import reduce
  from string import ascii_uppercase
  import numpy
  from scipy import stats
  from scipy.signal import detrend
  from ..utils import _check_option
label_desc: Use image node_id 9 for calling a global function with example usage: _parametric_ci(arr, ci) and returns: stats, mean,  sigma