NTPsec

ntp2.wiktel.com

Report generated: Sat Aug 8 16:45:07 2026 UTC
Start Time: Sat Aug 1 16:45:01 2026 UTC
End Time: Sat Aug 8 16:45:01 2026 UTC
Report Period: 7.0 days

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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 -66.603 -10.075 -6.268 0.645 3.493 4.928 17.649 9.761 15.003 2.971 -0.001 µs -5.646 21.37
Local Clock Frequency Offset -13.900 -13.793 -13.689 -13.333 -13.030 -12.849 -12.547 0.659 0.944 0.213 -13.345 ppm -2.592e+05 1.654e+07

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 0.631 1.382 1.876 3.664 6.222 7.712 34.158 4.346 6.330 1.356 3.807 µs 12.29 44.77

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 1.043 2.036 2.749 5.320 8.814 10.842 46.517 6.065 8.806 1.886 5.490 ppb 13.6 49.58

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 -66.603 -10.075 -6.268 0.645 3.493 4.928 17.649 9.761 15.003 2.971 -0.001 µs -5.646 21.37

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats 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 132.163.97.5

peer offset 132.163.97.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 132.163.97.5 -1.474 -1.458 -1.443 -1.084 2.309 2.339 2.363 3.752 3.797 1.515 -0.211 ms -3.905 6.975

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 132.246.11.238

peer offset 132.246.11.238 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 132.246.11.238 0.222 0.359 0.402 1.286 1.728 1.836 3.554 1.326 1.476 0.486 1.106 ms 5.874 14.58

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 134.84.84.84

peer offset 134.84.84.84 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 134.84.84.84 -2.926 -2.926 -0.833 -0.339 0.923 1.045 1.045 1.756 3.971 0.770 -0.223 ms -6.89 23.19

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 204.9.54.119

peer offset 204.9.54.119 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.9.54.119 -2.020 -2.012 -2.006 -1.022 -1.013 -1.004 2.440 0.992 1.008 0.316 -1.076 ms -96.28 501

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 2600:2600::99 (ntp1.wiktel.com)

peer offset 2600:2600::99 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2600:2600::99 (ntp1.wiktel.com) -378.983 -363.985 -357.221 -342.903 -327.496 -322.344 -312.856 29.725 41.641 9.058 -342.943 µs -5.88e+04 2.29e+06

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 2602:fd53:11e:123::1 (time1.mbix.ca)

peer offset 2602:fd53:11e:123::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2602:fd53:11e:123::1 (time1.mbix.ca) -442.809 -423.365 -407.358 -375.597 -347.377 -332.584 -319.781 59.981 90.781 18.497 -375.990 µs -9765 2.096e+05

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 2606:4700:f1::123 (time.cloudflare.com)

peer offset 2606:4700:f1::123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2606:4700:f1::123 (time.cloudflare.com) -4.267 -4.124 -1.138 -0.063 0.150 0.437 0.978 1.288 4.561 0.735 -0.222 ms -10.58 59.55

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 2607:f388::123:2 (ntp2.doit.wisc.edu)

peer offset 2607:f388::123:2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2607:f388::123:2 (ntp2.doit.wisc.edu) -3,702.822 -263.313 -79.010 -22.296 35.923 136.510 2,181.753 114.933 399.823 302.548 -43.788 µs -15.41 190.5

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) -66.604 -10.076 -6.269 0.646 3.494 4.929 17.650 9.763 15.005 2.972 -0.000 µs -5.645 21.36

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 132.163.97.5

peer jitter 132.163.97.5 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 132.163.97.5 8.007 15.228 21.332 59.965 365.998 388.874 3,217.801 344.666 373.646 191.241 164.506 µs 5.785 75.69

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 132.246.11.238

peer jitter 132.246.11.238 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 132.246.11.238 0.035 0.078 0.136 0.466 2.140 4.147 112.612 2.004 4.069 6.201 1.149 ms 11.07 171

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 134.84.84.84

peer jitter 134.84.84.84 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 134.84.84.84 0.000 0.000 0.000 6.959 92.508 708.084 708.084 92.508 708.084 99.121 31.787 µs 3.314 24.47

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 204.9.54.119

peer jitter 204.9.54.119 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.9.54.119 1.997 3.766 4.985 9.183 16.377 691.421 3,440.908 11.392 687.655 199.351 27.398 µs 10.49 162.3

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 2600:2600::99 (ntp1.wiktel.com)

peer jitter 2600:2600::99 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2600:2600::99 (ntp1.wiktel.com) 3.990 6.611 9.320 18.926 33.252 40.333 54.115 23.932 33.722 7.468 19.906 µs 10.22 31.67

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 2602:fd53:11e:123::1 (time1.mbix.ca)

peer jitter 2602:fd53:11e:123::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2602:fd53:11e:123::1 (time1.mbix.ca) 5.098 8.141 11.008 21.857 43.992 60.492 1,032.744 32.984 52.351 42.633 25.900 µs 18.59 415.6

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 2606:4700:f1::123 (time.cloudflare.com)

peer jitter 2606:4700:f1::123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2606:4700:f1::123 (time.cloudflare.com) 4.106 9.285 13.155 45.898 195.994 412.600 3,838.305 182.839 403.315 119.309 71.901 µs 16.05 460.9

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 2607:f388::123:2 (ntp2.doit.wisc.edu)

peer jitter 2607:f388::123:2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2607:f388::123:2 (ntp2.doit.wisc.edu) 0.006 0.009 0.012 0.023 0.042 0.076 16.748 0.030 0.067 0.710 0.066 ms 17.26 380.6

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) 0.154 0.607 0.973 3.262 7.879 10.932 65.344 6.906 10.325 2.240 3.685 µs 3.753 15.94

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 -13.900 -13.793 -13.689 -13.333 -13.030 -12.849 -12.547 0.659 0.944 0.213 -13.345 ppm -2.592e+05 1.654e+07
Local Clock Time Offset -66.603 -10.075 -6.268 0.645 3.493 4.928 17.649 9.761 15.003 2.971 -0.001 µs -5.646 21.37
Local RMS Frequency Jitter 1.043 2.036 2.749 5.320 8.814 10.842 46.517 6.065 8.806 1.886 5.490 ppb 13.6 49.58
Local RMS Time Jitter 0.631 1.382 1.876 3.664 6.222 7.712 34.158 4.346 6.330 1.356 3.807 µs 12.29 44.77
Server Jitter 132.163.97.5 8.007 15.228 21.332 59.965 365.998 388.874 3,217.801 344.666 373.646 191.241 164.506 µs 5.785 75.69
Server Jitter 132.246.11.238 0.035 0.078 0.136 0.466 2.140 4.147 112.612 2.004 4.069 6.201 1.149 ms 11.07 171
Server Jitter 134.84.84.84 0.000 0.000 0.000 6.959 92.508 708.084 708.084 92.508 708.084 99.121 31.787 µs 3.314 24.47
Server Jitter 204.9.54.119 1.997 3.766 4.985 9.183 16.377 691.421 3,440.908 11.392 687.655 199.351 27.398 µs 10.49 162.3
Server Jitter 2600:2600::99 (ntp1.wiktel.com) 3.990 6.611 9.320 18.926 33.252 40.333 54.115 23.932 33.722 7.468 19.906 µs 10.22 31.67
Server Jitter 2602:fd53:11e:123::1 (time1.mbix.ca) 5.098 8.141 11.008 21.857 43.992 60.492 1,032.744 32.984 52.351 42.633 25.900 µs 18.59 415.6
Server Jitter 2606:4700:f1::123 (time.cloudflare.com) 4.106 9.285 13.155 45.898 195.994 412.600 3,838.305 182.839 403.315 119.309 71.901 µs 16.05 460.9
Server Jitter 2607:f388::123:2 (ntp2.doit.wisc.edu) 0.006 0.009 0.012 0.023 0.042 0.076 16.748 0.030 0.067 0.710 0.066 ms 17.26 380.6
Server Jitter SHM(1) 0.154 0.607 0.973 3.262 7.879 10.932 65.344 6.906 10.325 2.240 3.685 µs 3.753 15.94
Server Offset 132.163.97.5 -1.474 -1.458 -1.443 -1.084 2.309 2.339 2.363 3.752 3.797 1.515 -0.211 ms -3.905 6.975
Server Offset 132.246.11.238 0.222 0.359 0.402 1.286 1.728 1.836 3.554 1.326 1.476 0.486 1.106 ms 5.874 14.58
Server Offset 134.84.84.84 -2.926 -2.926 -0.833 -0.339 0.923 1.045 1.045 1.756 3.971 0.770 -0.223 ms -6.89 23.19
Server Offset 204.9.54.119 -2.020 -2.012 -2.006 -1.022 -1.013 -1.004 2.440 0.992 1.008 0.316 -1.076 ms -96.28 501
Server Offset 2600:2600::99 (ntp1.wiktel.com) -378.983 -363.985 -357.221 -342.903 -327.496 -322.344 -312.856 29.725 41.641 9.058 -342.943 µs -5.88e+04 2.29e+06
Server Offset 2602:fd53:11e:123::1 (time1.mbix.ca) -442.809 -423.365 -407.358 -375.597 -347.377 -332.584 -319.781 59.981 90.781 18.497 -375.990 µs -9765 2.096e+05
Server Offset 2606:4700:f1::123 (time.cloudflare.com) -4.267 -4.124 -1.138 -0.063 0.150 0.437 0.978 1.288 4.561 0.735 -0.222 ms -10.58 59.55
Server Offset 2607:f388::123:2 (ntp2.doit.wisc.edu) -3,702.822 -263.313 -79.010 -22.296 35.923 136.510 2,181.753 114.933 399.823 302.548 -43.788 µs -15.41 190.5
Server Offset SHM(1) -66.604 -10.076 -6.269 0.646 3.494 4.929 17.650 9.763 15.005 2.972 -0.000 µs -5.645 21.36
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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