NTPsec

STR1clock

Report generated: Tue Oct 22 10:30:15 2019 UTC
Start Time: Mon Oct 21 10:30:10 2019 UTC
End Time: Tue Oct 22 10:30:10 2019 UTC
Report Period: 1.0 days

Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Time Offset -335.564 -31.026 -4.846 0.028 4.701 29.782 757.618 9.547 60.808 12.793 0.002 µs 7.208 659.8
Local Clock Frequency Offset -14.328 -6.940 -6.298 -5.499 -4.947 -4.172 9.169 1.351 2.768 0.622 -5.586 ppm -1024 1.055e+04

The time and frequency offsets between the ntpd calculated time and the local system clock. Showing frequency offset (red, in parts per million, scale on right) and the time offset (blue, in μs, scale on left). Quick changes in time offset will lead to larger frequency offsets.

These are fields 3 (time) and 4 (frequency) from the loopstats log file.



Local RMS Time Jitter

local jitter plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Time Jitter 0.249 0.392 0.468 1.206 19.091 46.411 269.581 18.623 46.019 10.534 4.520 µs 7.226 128.3

The RMS Jitter of the local clock offset. In other words, how fast the local clock offset is changing.

Lower is better. An ideal system would be a horizontal line at 0μs.

RMS jitter is field 5 in the loopstats log file.



Local RMS Frequency Jitter

local stability plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Frequency Jitter 1.750 2.537 3.097 11.613 171.482 394.254 2,675.208 168.385 391.717 91.108 41.092 ppb 6.943 128

The RMS Frequency Jitter (aka wander) of the local clock's frequency. In other words, how fast the local clock changes frequency.

Lower is better. An ideal clock would be a horizontal line at 0ppm.

RMS Frequency Jitter is field 6 in the loopstats log file.



Local Clock Time Offset Histogram

local offset histogram plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Offset -335.564 -31.026 -4.846 0.028 4.701 29.782 757.618 9.547 60.808 12.793 0.002 µs 7.208 659.8

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats log file.



Local Temperatures

local temps plot

Local temperatures. These will be site-specific depending upon what temperature sensors you collect data from. Temperature changes affect the local clock crystal frequency and stability. The math of how temperature changes frequency is complex, and also depends on crystal aging. So there is no easy way to correct for it in software. This is the single most important component of frequency drift.

The Local Temperatures are from field 3 from the tempstats log file.



Local Frequency/Temp

local freq temps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -14.328 -6.940 -6.298 -5.499 -4.947 -4.172 9.169 1.351 2.768 0.622 -5.586 ppm -1024 1.055e+04
Temp ZONE0 61.224 61.224 61.224 63.376 67.680 68.756 68.756 6.456 7.532 2.238 64.125 °C

The frequency offsets and temperatures. Showing frequency offset (red, in parts per million, scale on right) and the temperatures.

These are field 4 (frequency) from the loopstats log file, and field 3 from the tempstats log file.



Server Offsets

peer offsets plot

The offset of all refclocks and servers. This can be useful to see if offset changes are happening in a single clock or all clocks together.

Clock Offset is field 5 in the peerstats log file.



Server Offset 130.133.1.10

peer offset 130.133.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 130.133.1.10 -6.731 -6.049 -5.768 -4.401 0.672 45.649 55.249 6.440 51.698 7.595 -2.974 ms -0.8243 21.41

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 140.203.204.77

peer offset 140.203.204.77 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 140.203.204.77 -5.745 -5.552 -5.254 -3.173 -0.012 42.529 50.353 5.242 48.081 6.903 -1.980 ms -0.01091 21.59

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 150.214.94.10

peer offset 150.214.94.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 150.214.94.10 -6.185 -1.755 -1.377 -0.627 5.145 63.138 67.949 6.521 64.892 9.667 1.338 ms 2.248 18.77

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 150.214.94.5

peer offset 150.214.94.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 150.214.94.5 -1.834 -1.599 -1.277 -0.471 4.106 43.863 52.547 5.383 45.463 7.406 1.041 ms 2.177 18.08

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 158.227.98.15

peer offset 158.227.98.15 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 158.227.98.15 -1.811 -1.579 -1.110 0.612 9.755 49.065 52.679 10.864 50.644 7.860 2.278 ms 2.502 17.19

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 194.80.204.184

peer offset 194.80.204.184 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.80.204.184 -5.652 -5.353 -5.177 -2.963 5.954 54.792 59.064 11.131 60.145 9.040 -1.307 ms 0.4449 16.89

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 85.199.214.98

peer offset 85.199.214.98 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 85.199.214.98 -3.742 -3.649 -3.053 -0.846 6.093 53.562 60.615 9.146 57.211 9.883 1.078 ms 1.323 12.99

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset SHM(0)

peer offset SHM(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset SHM(0) -5.616 -2.647 -1.323 2.312 7.365 8.554 9.589 8.688 11.201 2.753 2.637 ms 0.07815 2.307

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset SHM(1)

peer offset SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset SHM(1) -973.408 -736.676 -31.248 31.473 88.310 145.079 262.697 119.558 881.755 124.673 13.586 µs -8.617 56.1

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Jitters

peer jitters plot

The RMS Jitter of all refclocks and servers. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 130.133.1.10

peer jitter 130.133.1.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 130.133.1.10 0.370 0.429 0.889 7.372 53.005 87.051 150.984 52.117 86.622 19.838 15.584 ms 2.357 14.55

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 140.203.204.77

peer jitter 140.203.204.77 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 140.203.204.77 0.437 0.568 1.022 6.413 65.541 144.747 163.783 64.519 144.178 24.893 17.307 ms 2.084 11.41

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 150.214.94.10

peer jitter 150.214.94.10 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 150.214.94.10 0.505 0.667 1.067 6.448 49.748 77.298 92.932 48.681 76.631 16.216 13.111 ms 1.826 7.775

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 150.214.94.5

peer jitter 150.214.94.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 150.214.94.5 0.359 0.481 0.866 6.314 54.064 77.516 142.841 53.198 77.036 19.198 15.616 ms 1.53 8.261

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 158.227.98.15

peer jitter 158.227.98.15 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 158.227.98.15 0.344 0.554 0.777 4.969 48.442 103.361 159.408 47.664 102.807 22.405 14.197 ms 2.292 13.82

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 194.80.204.184

peer jitter 194.80.204.184 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.80.204.184 0.443 0.500 0.714 4.189 54.820 85.019 129.029 54.105 84.519 19.404 13.739 ms 1.696 8.921

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 85.199.214.98

peer jitter 85.199.214.98 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 85.199.214.98 0.351 0.553 0.876 6.445 82.469 152.115 158.347 81.593 151.562 30.087 17.718 ms 1.908 9.155

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter SHM(0)

peer jitter SHM(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(0) 0.162 0.247 0.355 0.945 2.272 2.935 4.022 1.916 2.688 0.615 1.094 ms 3.913 11.74

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter SHM(1)

peer jitter SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(1) 0.081 0.235 0.330 0.793 21.414 66.017 722.822 21.084 65.782 15.585 4.431 µs 12.4 392.2

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -14.328 -6.940 -6.298 -5.499 -4.947 -4.172 9.169 1.351 2.768 0.622 -5.586 ppm -1024 1.055e+04
Local Clock Time Offset -335.564 -31.026 -4.846 0.028 4.701 29.782 757.618 9.547 60.808 12.793 0.002 µs 7.208 659.8
Local RMS Frequency Jitter 1.750 2.537 3.097 11.613 171.482 394.254 2,675.208 168.385 391.717 91.108 41.092 ppb 6.943 128
Local RMS Time Jitter 0.249 0.392 0.468 1.206 19.091 46.411 269.581 18.623 46.019 10.534 4.520 µs 7.226 128.3
Server Jitter 130.133.1.10 0.370 0.429 0.889 7.372 53.005 87.051 150.984 52.117 86.622 19.838 15.584 ms 2.357 14.55
Server Jitter 140.203.204.77 0.437 0.568 1.022 6.413 65.541 144.747 163.783 64.519 144.178 24.893 17.307 ms 2.084 11.41
Server Jitter 150.214.94.10 0.505 0.667 1.067 6.448 49.748 77.298 92.932 48.681 76.631 16.216 13.111 ms 1.826 7.775
Server Jitter 150.214.94.5 0.359 0.481 0.866 6.314 54.064 77.516 142.841 53.198 77.036 19.198 15.616 ms 1.53 8.261
Server Jitter 158.227.98.15 0.344 0.554 0.777 4.969 48.442 103.361 159.408 47.664 102.807 22.405 14.197 ms 2.292 13.82
Server Jitter 194.80.204.184 0.443 0.500 0.714 4.189 54.820 85.019 129.029 54.105 84.519 19.404 13.739 ms 1.696 8.921
Server Jitter 85.199.214.98 0.351 0.553 0.876 6.445 82.469 152.115 158.347 81.593 151.562 30.087 17.718 ms 1.908 9.155
Server Jitter SHM(0) 0.162 0.247 0.355 0.945 2.272 2.935 4.022 1.916 2.688 0.615 1.094 ms 3.913 11.74
Server Jitter SHM(1) 0.081 0.235 0.330 0.793 21.414 66.017 722.822 21.084 65.782 15.585 4.431 µs 12.4 392.2
Server Offset 130.133.1.10 -6.731 -6.049 -5.768 -4.401 0.672 45.649 55.249 6.440 51.698 7.595 -2.974 ms -0.8243 21.41
Server Offset 140.203.204.77 -5.745 -5.552 -5.254 -3.173 -0.012 42.529 50.353 5.242 48.081 6.903 -1.980 ms -0.01091 21.59
Server Offset 150.214.94.10 -6.185 -1.755 -1.377 -0.627 5.145 63.138 67.949 6.521 64.892 9.667 1.338 ms 2.248 18.77
Server Offset 150.214.94.5 -1.834 -1.599 -1.277 -0.471 4.106 43.863 52.547 5.383 45.463 7.406 1.041 ms 2.177 18.08
Server Offset 158.227.98.15 -1.811 -1.579 -1.110 0.612 9.755 49.065 52.679 10.864 50.644 7.860 2.278 ms 2.502 17.19
Server Offset 194.80.204.184 -5.652 -5.353 -5.177 -2.963 5.954 54.792 59.064 11.131 60.145 9.040 -1.307 ms 0.4449 16.89
Server Offset 85.199.214.98 -3.742 -3.649 -3.053 -0.846 6.093 53.562 60.615 9.146 57.211 9.883 1.078 ms 1.323 12.99
Server Offset SHM(0) -5.616 -2.647 -1.323 2.312 7.365 8.554 9.589 8.688 11.201 2.753 2.637 ms 0.07815 2.307
Server Offset SHM(1) -973.408 -736.676 -31.248 31.473 88.310 145.079 262.697 119.558 881.755 124.673 13.586 µs -8.617 56.1
Temp ZONE0 61.224 61.224 61.224 63.376 67.680 68.756 68.756 6.456 7.532 2.238 64.125 °C
Summary as CSV file

Glossary:

frequency offset:
The difference between the ntpd calculated frequency and the local system clock frequency (usually in parts per million, ppm)
jitter, dispersion:
The short term change in a value. NTP measures Local Time Jitter, Refclock Jitter, and Server Jitter in seconds. Local Frequency Jitter is in ppm or ppb.
kurtosis, Kurt:
The kurtosis of a random variable X is the fourth standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of kurtosis. A normal distribution has a kurtosis of three. NIST describes a kurtosis over three as "heavy tailed" and one under three as "light tailed".
ms, millisecond:
One thousandth of a second = 0.001 seconds, 1e-3 seconds
mu, mean:
The arithmetic mean: the sum of all the values divided by the number of values. The formula for mu is: "mu = (∑xi) / N". Where xi denotes the data points and N is the number of data points.
ns, nanosecond:
One billionth of a second, also one thousandth of a microsecond, 0.000000001 seconds and 1e-9 seconds.
percentile:
The value below which a given percentage of values fall.
ppb, parts per billion:
Ratio between two values. These following are all the same: 1 ppb, one in one billion, 1/1,000,000,000, 0.000,000,001, 1e-9 and 0.000,000,1%
ppm, parts per million:
Ratio between two values. These following are all the same: 1 ppm, one in one million, 1/1,000,000, 0.000,001, and 0.000,1%
‰, parts per thousand:
Ratio between two values. These following are all the same: 1 ‰. one in one thousand, 1/1,000, 0.001, and 0.1%
refclock:
Reference clock, a local GPS module or other local source of time.
remote clock:
Any clock reached over the network, LAN or WAN. Also called a peer or server.
time offset:
The difference between the ntpd calculated time and the local system clock's time. Also called phase offset.
σ, sigma:
Sigma denotes the standard deviation (SD) and is centered on the arithmetic mean of the data set. The SD is simply the square root of the variance of the data set. Two sigma is simply twice the standard deviation. Three sigma is three times sigma. Smaller is better.
The formula for sigma is: "σ = √[ ∑(xi-mu)^2 / N ]". Where xi denotes the data points and N is the number of data points.
skewness, Skew:
The skewness of a random variable X is the third standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of skewness. Wikipedia describes it best: "The qualitative interpretation of the skew is complicated and unintuitive."
A normal distribution has a skewness of zero.
upstream clock:
Any server or reference clock used as a source of time.
µs, us, microsecond:
One millionth of a second, also one thousandth of a millisecond, 0.000,001 seconds, and 1e-6 seconds.



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