/**
  * Get the Variance of all the stats that are watched, for all the stats added with add() since
  * the creation of this <tt>HammerSummaryStats</tt>
  *
  * @return The Variance of all the stats JSON.
  */
 public String getAggregateVarianceJSON() {
   String str =
       String.format(
           FakeUserStats.jsonMediaStreamStatsTemplate,
           -1, // ssrc not needed here
           aggregateDownloadJitterMs.getVariance(),
           aggregateDownloadPercentLoss.getVariance(),
           aggregateDownloadRateKiloBitPerSec.getVariance(),
           aggregateJitterBufferDelayMs.getVariance(),
           aggregateJitterBufferDelayPackets.getVariance(),
           aggregateNbDiscarded.getVariance(),
           aggregateNbDiscardedFull.getVariance(),
           aggregateNbDiscardedLate.getVariance(),
           aggregateNbDiscardedReset.getVariance(),
           aggregateNbDiscardedShrink.getVariance(),
           aggregateNbFec.getVariance(),
           aggregateNbPackets.getVariance(),
           aggregateNbPacketsLost.getVariance(),
           aggregateNbReceivedBytes.getVariance(),
           aggregateNbSentBytes.getVariance(),
           aggregatePacketQueueCountPackets.getVariance(),
           aggregatePacketQueueSize.getVariance(),
           aggregatePercentDiscarded.getVariance(),
           aggregateRttMs.getVariance(),
           aggregateUploadJitterMs.getVariance(),
           aggregateUploadPercentLoss.getVariance(),
           aggregateUploadRateKiloBitPerSec.getVariance());
   return str;
 }