Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_statfun_mean”.

  FT_STATFUN_MEAN computes the mean over all replications for each of the
  observations (i.e. channel-time-frequency points or voxels).
  This function does not depend on the experimental design and cannot be used for any
  statistical testing. However, it serves as example how you can use the statistical
  framework in FieldTrip to perform a simple (or more complex) task, without having
  to worry about the representation of the data. The output of FT_TIMELOCKSTATISTICS,
  FT_FREQSTATISTICS or FT_SOURCESTATISTICS will be an appropriate structure, that
  contains the result of the computation inside this function in the stat field.
  See also FT_STATFUN_DIFF for another example statfun