Using Workbench Command

WEIGHTED SPATIAL STATISTICS ON A VOLUME FILE
   wb_command -volume-weighted-stats
      <volume-in> - the input volume

      [-weight-volume] - use weights from a volume file
         <weight-volume> - volume file containing the weights

         [-match-maps] - each subvolume of input uses the corresponding
            subvolume from the weights file

      [-subvolume] - only display output for one subvolume
         <subvolume> - the subvolume number or name

      [-roi] - only consider data inside an roi
         <roi-volume> - the roi, as a volume file

         [-match-maps] - each subvolume of input uses the corresponding
            subvolume from the roi file

      [-mean] - compute weighted mean

      [-stdev] - compute weighted standard deviation

         [-sample] - estimate population stdev from the sample

      [-percentile] - compute weighted percentile
         <percent> - the percentile to find, must be between 0 and 100

      [-sum] - compute weighted sum

      [-show-map-name] - print map index and name before each output

      For each subvolume of the input, a line of text is printed, resulting
      from the specified operation.  If -weight-volume is not specified, each
      voxel's volume is used.  Use -subvolume to only give output for a single
      subvolume.  If the -roi option is used without -match-maps, then each
      line will contain as many numbers as there are maps in the ROI file,
      separated by tab characters.  Exactly one of -mean, -stdev, -percentile
      or -sum must be specified.

      Using -sum without -weight-volume is equivalent to integrating with
      respect to volume.