instance method get_confidence

# File actionmailer/lib/action_mailer/vendor/tmail-1.2.7/tmail/vendor/rchardet-1.3/lib/rchardet/jpcntx.rb, line 170
    def get_confidence
      # This is just one way to calculate confidence. It works well for me.
      if @_mTotalRel > MINIMUM_DATA_THRESHOLD
        return (@_mTotalRel - @_mRelSample[0]) / @_mTotalRel
      else
        return DONT_KNOW
      end
    end