public void writeIntervalSummaryData(StatisticsSet intervalStatistics, boolean firstCall) {
		for (Entry<String, StatisticExpression> each : getExpressionEntrySet()) {
			if (firstCall) {
				double doubleValue = each.getValue().getDoubleValue(intervalStatistics);
				writeReportData(each.getKey() + REPORT_DATA, formatValue(getRealDoubleValue(doubleValue)));
			} else {
				writeReportData(each.getKey() + REPORT_DATA, "null");
			}
		}
		writeReportData("Vuser" + REPORT_DATA, formatValue(runningThread));
	}
Write the total test interval statistic data into file.

@param intervalStatistics interval statistics
@param firstCall          true if it's the last call of consecutive calls in a single
                          sampling
ngrinder-core/src/main/java/net/grinder/SingleConsole.java