code: public double getErrorRate(String intervalName){
  		long tr = getTotalRequests(intervalName);
  		double errorRate = tr == 0? 0:((double)getErrors(intervalName))/tr;
  		return (double)((int)(errorRate * 10000))/100;
  	}
docs: Returns the error rate. This value was previously calculated in decorator, but we moved it into the stats object to be able to define threshold on top of it.
  @param intervalName name of the interval.
  @return the error rate in percent.