NTPsec

ntp1.wiktel.com

Report generated: Mon Sep 15 22:53:01 2025 UTC
Start Time: Sun Sep 14 22:53:00 2025 UTC
End Time: Mon Sep 15 22:53:00 2025 UTC
Report Period: 1.0 days

Top   Daily Stats   Weekly Stats  

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 -10.305 -4.472 -3.351 -0.156 3.830 5.772 9.303 7.181 10.244 2.264 -0.009 µs -3.686 8.786
Local Clock Frequency Offset 17.358 17.365 17.390 17.482 17.534 17.575 17.593 0.144 0.209 0.042 17.475 ppm 6.906e+07 2.834e+10

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 0.341 0.476 0.566 0.813 1.475 2.294 3.655 0.909 1.818 0.323 0.882 µs 13.17 60.61

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 0.177 0.259 0.346 0.893 1.964 2.656 3.810 1.618 2.397 0.524 0.974 ppb 4.496 15.13

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 -10.305 -4.472 -3.351 -0.156 3.830 5.772 9.303 7.181 10.244 2.264 -0.009 µs -3.686 8.786

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 128.101.101.101

peer offset 128.101.101.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 128.101.101.101 -70.375 -62.722 -29.798 41.488 115.382 150.335 165.580 145.180 213.057 45.212 44.485 µs -0.06654 2.786

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 128.138.141.177

peer offset 128.138.141.177 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 128.138.141.177 -307.892 -199.179 -123.859 2.615 327.447 486.071 601.844 451.306 685.250 142.078 41.283 µs -1.398 4.41

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 209.87.233.53

peer offset 209.87.233.53 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 209.87.233.53 -7.025 -3.547 -1.144 1.344 3.721 7.568 8.193 4.865 11.114 1.687 1.385 ms -0.4763 7.111

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::2 (time2.mbix.ca)

peer offset 2602:fd53:11e:123::2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2602:fd53:11e:123::2 (time2.mbix.ca) -87.881 -83.534 -69.140 -34.994 -2.595 4.353 11.556 66.545 87.887 20.746 -35.313 µs -27.92 100.3

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::1 (time.cloudflare.com)

peer offset 2606:4700:f1::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2606:4700:f1::1 (time.cloudflare.com) -182.724 -173.261 -111.498 -14.342 87.022 109.284 122.599 198.520 282.545 59.777 -15.316 µs -5.983 16.38

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) -178.130 -178.130 -145.843 -18.125 77.448 135.894 135.894 223.291 314.024 77.306 -34.193 µs -7.396 19.09

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:f128:1:3::dd1

peer offset 2607:f128:1:3::dd1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2607:f128:1:3::dd1 -284.268 -282.787 -265.276 -229.340 -186.781 -168.965 -151.340 78.495 113.822 23.371 -227.863 µs -1274 1.404e+04

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::123:1 (ntp1.doit.wisc.edu)

peer offset 2607:f388::123:1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -540.369 -508.967 -434.787 -372.071 -219.141 -118.469 -102.769 215.646 390.498 64.104 -361.346 µs -310.6 2170

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 PPS(0)

peer offset PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset PPS(0) -10.306 -4.473 -3.352 -0.157 3.831 5.773 9.304 7.183 10.246 2.265 -0.009 µs -3.686 8.785

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 128.101.101.101

peer jitter 128.101.101.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 128.101.101.101 6.085 8.060 11.549 25.779 63.017 95.488 127.576 51.468 87.428 17.358 30.387 µs 4.518 18.19

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 128.138.141.177

peer jitter 128.138.141.177 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 128.138.141.177 0.214 0.263 0.374 0.618 0.869 5.814 6.029 0.495 5.551 0.562 0.675 ms 9.259 88.72

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 209.87.233.53

peer jitter 209.87.233.53 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 209.87.233.53 1.513 2.354 3.506 9.955 26.932 67.233 67.503 23.426 64.878 10.342 12.340 ms 3.983 20.16

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::2 (time2.mbix.ca)

peer jitter 2602:fd53:11e:123::2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2602:fd53:11e:123::2 (time2.mbix.ca) 5.496 9.924 15.508 27.618 51.176 60.324 63.378 35.668 50.400 10.581 29.275 µs 11.71 38.46

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::1 (time.cloudflare.com)

peer jitter 2606:4700:f1::1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 9.978 11.583 13.384 30.095 119.248 173.336 225.194 105.864 161.753 35.396 42.950 µs 2.856 10.78

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) 10.159 10.159 14.452 35.173 108.420 163.947 163.947 93.968 153.788 33.404 49.142 µs 2.95 9.071

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:f128:1:3::dd1

peer jitter 2607:f128:1:3::dd1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2607:f128:1:3::dd1 13.753 14.938 17.702 31.924 61.784 79.905 104.048 44.082 64.967 13.765 34.360 µs 9.345 34.12

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::123:1 (ntp1.doit.wisc.edu)

peer jitter 2607:f388::123:1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 5.715 9.776 12.039 23.079 49.865 68.384 314.272 37.826 58.608 25.295 27.395 µs 9.091 99.74

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 PPS(0)

peer jitter PPS(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter PPS(0) 0.133 0.304 0.421 0.840 1.873 2.759 7.009 1.452 2.455 0.520 0.961 µs 6.023 34.36

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 17.358 17.365 17.390 17.482 17.534 17.575 17.593 0.144 0.209 0.042 17.475 ppm 6.906e+07 2.834e+10
Local Clock Time Offset -10.305 -4.472 -3.351 -0.156 3.830 5.772 9.303 7.181 10.244 2.264 -0.009 µs -3.686 8.786
Local RMS Frequency Jitter 0.177 0.259 0.346 0.893 1.964 2.656 3.810 1.618 2.397 0.524 0.974 ppb 4.496 15.13
Local RMS Time Jitter 0.341 0.476 0.566 0.813 1.475 2.294 3.655 0.909 1.818 0.323 0.882 µs 13.17 60.61
Server Jitter 128.101.101.101 6.085 8.060 11.549 25.779 63.017 95.488 127.576 51.468 87.428 17.358 30.387 µs 4.518 18.19
Server Jitter 128.138.141.177 0.214 0.263 0.374 0.618 0.869 5.814 6.029 0.495 5.551 0.562 0.675 ms 9.259 88.72
Server Jitter 209.87.233.53 1.513 2.354 3.506 9.955 26.932 67.233 67.503 23.426 64.878 10.342 12.340 ms 3.983 20.16
Server Jitter 2602:fd53:11e:123::2 (time2.mbix.ca) 5.496 9.924 15.508 27.618 51.176 60.324 63.378 35.668 50.400 10.581 29.275 µs 11.71 38.46
Server Jitter 2606:4700:f1::1 (time.cloudflare.com) 9.978 11.583 13.384 30.095 119.248 173.336 225.194 105.864 161.753 35.396 42.950 µs 2.856 10.78
Server Jitter 2606:4700:f1::123 (time.cloudflare.com) 10.159 10.159 14.452 35.173 108.420 163.947 163.947 93.968 153.788 33.404 49.142 µs 2.95 9.071
Server Jitter 2607:f128:1:3::dd1 13.753 14.938 17.702 31.924 61.784 79.905 104.048 44.082 64.967 13.765 34.360 µs 9.345 34.12
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 5.715 9.776 12.039 23.079 49.865 68.384 314.272 37.826 58.608 25.295 27.395 µs 9.091 99.74
Server Jitter PPS(0) 0.133 0.304 0.421 0.840 1.873 2.759 7.009 1.452 2.455 0.520 0.961 µs 6.023 34.36
Server Offset 128.101.101.101 -70.375 -62.722 -29.798 41.488 115.382 150.335 165.580 145.180 213.057 45.212 44.485 µs -0.06654 2.786
Server Offset 128.138.141.177 -307.892 -199.179 -123.859 2.615 327.447 486.071 601.844 451.306 685.250 142.078 41.283 µs -1.398 4.41
Server Offset 209.87.233.53 -7.025 -3.547 -1.144 1.344 3.721 7.568 8.193 4.865 11.114 1.687 1.385 ms -0.4763 7.111
Server Offset 2602:fd53:11e:123::2 (time2.mbix.ca) -87.881 -83.534 -69.140 -34.994 -2.595 4.353 11.556 66.545 87.887 20.746 -35.313 µs -27.92 100.3
Server Offset 2606:4700:f1::1 (time.cloudflare.com) -182.724 -173.261 -111.498 -14.342 87.022 109.284 122.599 198.520 282.545 59.777 -15.316 µs -5.983 16.38
Server Offset 2606:4700:f1::123 (time.cloudflare.com) -178.130 -178.130 -145.843 -18.125 77.448 135.894 135.894 223.291 314.024 77.306 -34.193 µs -7.396 19.09
Server Offset 2607:f128:1:3::dd1 -284.268 -282.787 -265.276 -229.340 -186.781 -168.965 -151.340 78.495 113.822 23.371 -227.863 µs -1274 1.404e+04
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -540.369 -508.967 -434.787 -372.071 -219.141 -118.469 -102.769 215.646 390.498 64.104 -361.346 µs -310.6 2170
Server Offset PPS(0) -10.306 -4.473 -3.352 -0.157 3.831 5.773 9.304 7.183 10.246 2.265 -0.009 µs -3.686 8.785
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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