/**
  * Get the Standard Deviation of all the stats that are watched, for all the stats added with
  * add() since the last call to clear() in JSON.
  *
  * @return The Standard Deviation of all the stats since last clear() in JSON.
  */
 public String getStandardDeviationJSON() {
   String str =
       String.format(
           FakeUserStats.jsonMediaStreamStatsTemplate,
           -1, // ssrc not needed here
           downloadJitterMs.getStandardDeviation(),
           downloadPercentLoss.getStandardDeviation(),
           downloadRateKiloBitPerSec.getStandardDeviation(),
           jitterBufferDelayMs.getStandardDeviation(),
           jitterBufferDelayPackets.getStandardDeviation(),
           nbDiscarded.getStandardDeviation(),
           nbDiscardedFull.getStandardDeviation(),
           nbDiscardedLate.getStandardDeviation(),
           nbDiscardedReset.getStandardDeviation(),
           nbDiscardedShrink.getStandardDeviation(),
           nbFec.getStandardDeviation(),
           nbPackets.getStandardDeviation(),
           nbPacketsLost.getStandardDeviation(),
           nbReceivedBytes.getStandardDeviation(),
           nbSentBytes.getStandardDeviation(),
           packetQueueCountPackets.getStandardDeviation(),
           packetQueueSize.getStandardDeviation(),
           percentDiscarded.getStandardDeviation(),
           rttMs.getStandardDeviation(),
           uploadJitterMs.getStandardDeviation(),
           uploadPercentLoss.getStandardDeviation(),
           uploadRateKiloBitPerSec.getStandardDeviation());
   return str;
 }