code: public static double standardDeviationFromMean(
          DoubleTuple t, double mean)
      {
          double variance = variance(t, mean);
          return Math.sqrt(variance);
      }
docs: Returns the standard deviation of the given tuple.
  The method will compute {@link #variance(DoubleTuple)}, return
  the square root of this value.
  
  @param t The input tuple
  @param mean The mean, which may have been computed before with
  {@link #arithmeticMean(DoubleTuple)}
  @return The standard deviation