public double stdDev(){
  double avg=avgRate();
  double sum=0.0;
  for (  Sample s : samples) {
    sum+=Math.pow((double)s.rate() - avg,2);
  }
  double variance=sum / (double)samples.size();
  return Math.sqrt(variance);
}

public double stdDev ( ) { double avg = avgRate ( ) ; double sum = 0.0 ; for ( Sample s : samples ) { sum += Math . pow ( ( double ) s . rate ( ) - avg , 2 ) ; } double variance = sum / ( double ) samples . size ( ) ; return Math . sqrt ( variance ) ; }
returns the standard deviation of the message rates in the samplegroup .
