NTPsec

crane3.services.mbix.ca

Report generated: Mon May 4 23:53:02 2026 UTC
Start Time: Sun May 3 23:53:02 2026 UTC
End Time: Mon May 4 23:53:02 2026 UTC
Report Period: 1.0 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 -45.425 -30.531 -22.553 -4.299 34.166 43.273 71.635 56.719 73.804 17.353 -0.028 µs -3.257 6.994
Local Clock Frequency Offset 78.250 78.269 78.286 78.439 78.575 78.602 78.655 0.290 0.333 0.096 78.431 ppm 5.361e+08 4.355e+11

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 7.830 10.559 13.343 22.637 33.984 38.050 46.101 20.641 27.491 6.326 23.098 µs 26.85 97

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 3.007 4.039 4.978 8.103 11.645 12.619 14.732 6.667 8.580 2.062 8.215 ppb 35.6 136.2

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 -45.425 -30.531 -22.553 -4.299 34.166 43.273 71.635 56.719 73.804 17.353 -0.028 µs -3.257 6.994

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 78.250 78.269 78.286 78.439 78.575 78.602 78.655 0.290 0.333 0.096 78.431 ppm 5.361e+08 4.355e+11
Temp LM0 35.000 35.000 35.000 37.000 39.000 40.000 41.000 4.000 5.000 1.164 36.958 °C
Temp LM1 32.000 33.000 33.000 35.000 37.000 37.000 38.000 4.000 4.000 1.113 34.876 °C
Temp LM10 34.000 34.000 34.000 36.000 37.000 38.000 38.000 3.000 4.000 0.865 35.696 °C
Temp LM2 31.000 31.000 32.000 33.000 35.000 36.000 36.000 3.000 5.000 1.064 33.378 °C
Temp LM3 35.000 35.000 35.000 37.000 39.000 40.000 40.000 4.000 5.000 1.168 37.007 °C
Temp LM4 33.000 34.000 34.000 35.000 37.000 38.000 38.000 3.000 4.000 0.829 35.353 °C
Temp LM5 62.000 62.000 62.000 63.000 64.000 64.000 64.000 2.000 2.000 0.569 62.731 °C
Temp LM6 40.000 40.000 41.000 42.000 43.000 43.000 43.000 2.000 3.000 0.638 41.823 °C
Temp LM7 38.000 38.000 39.000 40.000 41.000 42.000 43.000 2.000 4.000 0.803 40.194 °C
Temp LM8 39.000 39.000 40.000 41.000 42.000 43.000 43.000 2.000 4.000 0.766 41.230 °C
Temp LM9 37.000 38.000 39.000 40.000 41.000 42.000 43.000 2.000 4.000 0.819 39.809 °C
Temp ZONE0 40.000 40.000 41.000 42.000 43.000 43.000 44.000 2.000 3.000 0.745 41.919 °C
Temp ZONE1 35.000 35.000 36.000 37.000 39.000 40.000 40.000 3.000 5.000 1.227 37.258 °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 132.246.11.227

peer offset 132.246.11.227 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 132.246.11.227 1.707 1.975 2.005 2.100 2.198 2.229 2.314 0.194 0.254 0.061 2.101 ms 3.79e+04 1.275e+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 142.3.100.2

peer offset 142.3.100.2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 142.3.100.2 -85.600 -73.000 -57.337 -10.289 41.045 61.789 68.441 98.382 134.789 29.075 -8.692 µs -5.944 14.96

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::199 (ntp2.wiktel.com)

peer offset 2600:2600::199 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2600:2600::199 (ntp2.wiktel.com) 301.584 313.960 335.307 367.582 399.249 408.807 429.256 63.942 94.847 19.948 367.244 µs 5329 9.369e+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 2602:fde5:2a::13

peer offset 2602:fde5:2a::13 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2602:fde5:2a::13 1.439 1.439 1.451 1.492 2.127 2.136 2.150 0.676 0.697 0.300 1.703 ms 116.3 617.9

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) -2.712 -2.585 -2.406 -2.111 -1.876 0.076 0.192 0.530 2.662 0.449 -2.049 ms -185.3 1077

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) -735.906 -719.822 -670.658 -460.973 -357.117 -272.744 -245.130 313.541 447.078 85.550 -475.815 µs -303.1 2141

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) -45.426 -30.532 -22.554 -4.300 34.167 43.274 71.636 56.721 73.806 17.354 -0.028 µs -3.257 6.994

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 132.246.11.227

peer jitter 132.246.11.227 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 132.246.11.227 0.036 0.051 0.076 0.298 1.311 2.118 5.959 1.235 2.067 0.494 0.434 ms 5.295 53.02

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 142.3.100.2

peer jitter 142.3.100.2 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 142.3.100.2 0.012 0.016 0.021 0.038 0.085 0.842 91.932 0.065 0.826 7.630 0.691 ms 8.392 104.4

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::199 (ntp2.wiktel.com)

peer jitter 2600:2600::199 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2600:2600::199 (ntp2.wiktel.com) 7.623 9.974 11.957 23.309 48.006 66.232 81.153 36.049 56.258 11.447 25.813 µs 7.129 24.57

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:fde5:2a::13

peer jitter 2602:fde5:2a::13 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2602:fde5:2a::13 7.333 8.848 13.110 30.646 619.958 645.872 668.356 606.848 637.024 239.534 184.656 µs 0.2303 1.489

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) 0.008 0.010 0.015 0.039 0.151 1.144 2.457 0.136 1.134 0.223 0.074 ms 6.615 64.85

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) 5.913 9.503 14.507 26.673 79.878 606.972 807.850 65.371 597.469 101.473 49.203 µs 3.473 21.81

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) 2.947 5.557 8.330 21.592 42.383 51.436 80.945 34.053 45.879 10.297 22.987 µs 6.274 18.33

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 78.250 78.269 78.286 78.439 78.575 78.602 78.655 0.290 0.333 0.096 78.431 ppm 5.361e+08 4.355e+11
Local Clock Time Offset -45.425 -30.531 -22.553 -4.299 34.166 43.273 71.635 56.719 73.804 17.353 -0.028 µs -3.257 6.994
Local RMS Frequency Jitter 3.007 4.039 4.978 8.103 11.645 12.619 14.732 6.667 8.580 2.062 8.215 ppb 35.6 136.2
Local RMS Time Jitter 7.830 10.559 13.343 22.637 33.984 38.050 46.101 20.641 27.491 6.326 23.098 µs 26.85 97
Server Jitter 132.246.11.227 0.036 0.051 0.076 0.298 1.311 2.118 5.959 1.235 2.067 0.494 0.434 ms 5.295 53.02
Server Jitter 142.3.100.2 0.012 0.016 0.021 0.038 0.085 0.842 91.932 0.065 0.826 7.630 0.691 ms 8.392 104.4
Server Jitter 2600:2600::199 (ntp2.wiktel.com) 7.623 9.974 11.957 23.309 48.006 66.232 81.153 36.049 56.258 11.447 25.813 µs 7.129 24.57
Server Jitter 2602:fde5:2a::13 7.333 8.848 13.110 30.646 619.958 645.872 668.356 606.848 637.024 239.534 184.656 µs 0.2303 1.489
Server Jitter 2606:4700:f1::123 (time.cloudflare.com) 0.008 0.010 0.015 0.039 0.151 1.144 2.457 0.136 1.134 0.223 0.074 ms 6.615 64.85
Server Jitter 2607:f388::123:1 (ntp1.doit.wisc.edu) 5.913 9.503 14.507 26.673 79.878 606.972 807.850 65.371 597.469 101.473 49.203 µs 3.473 21.81
Server Jitter PPS(0) 2.947 5.557 8.330 21.592 42.383 51.436 80.945 34.053 45.879 10.297 22.987 µs 6.274 18.33
Server Offset 132.246.11.227 1.707 1.975 2.005 2.100 2.198 2.229 2.314 0.194 0.254 0.061 2.101 ms 3.79e+04 1.275e+06
Server Offset 142.3.100.2 -85.600 -73.000 -57.337 -10.289 41.045 61.789 68.441 98.382 134.789 29.075 -8.692 µs -5.944 14.96
Server Offset 2600:2600::199 (ntp2.wiktel.com) 301.584 313.960 335.307 367.582 399.249 408.807 429.256 63.942 94.847 19.948 367.244 µs 5329 9.369e+04
Server Offset 2602:fde5:2a::13 1.439 1.439 1.451 1.492 2.127 2.136 2.150 0.676 0.697 0.300 1.703 ms 116.3 617.9
Server Offset 2606:4700:f1::123 (time.cloudflare.com) -2.712 -2.585 -2.406 -2.111 -1.876 0.076 0.192 0.530 2.662 0.449 -2.049 ms -185.3 1077
Server Offset 2607:f388::123:1 (ntp1.doit.wisc.edu) -735.906 -719.822 -670.658 -460.973 -357.117 -272.744 -245.130 313.541 447.078 85.550 -475.815 µs -303.1 2141
Server Offset PPS(0) -45.426 -30.532 -22.554 -4.300 34.167 43.274 71.636 56.721 73.806 17.354 -0.028 µs -3.257 6.994
Temp LM0 35.000 35.000 35.000 37.000 39.000 40.000 41.000 4.000 5.000 1.164 36.958 °C
Temp LM1 32.000 33.000 33.000 35.000 37.000 37.000 38.000 4.000 4.000 1.113 34.876 °C
Temp LM10 34.000 34.000 34.000 36.000 37.000 38.000 38.000 3.000 4.000 0.865 35.696 °C
Temp LM2 31.000 31.000 32.000 33.000 35.000 36.000 36.000 3.000 5.000 1.064 33.378 °C
Temp LM3 35.000 35.000 35.000 37.000 39.000 40.000 40.000 4.000 5.000 1.168 37.007 °C
Temp LM4 33.000 34.000 34.000 35.000 37.000 38.000 38.000 3.000 4.000 0.829 35.353 °C
Temp LM5 62.000 62.000 62.000 63.000 64.000 64.000 64.000 2.000 2.000 0.569 62.731 °C
Temp LM6 40.000 40.000 41.000 42.000 43.000 43.000 43.000 2.000 3.000 0.638 41.823 °C
Temp LM7 38.000 38.000 39.000 40.000 41.000 42.000 43.000 2.000 4.000 0.803 40.194 °C
Temp LM8 39.000 39.000 40.000 41.000 42.000 43.000 43.000 2.000 4.000 0.766 41.230 °C
Temp LM9 37.000 38.000 39.000 40.000 41.000 42.000 43.000 2.000 4.000 0.819 39.809 °C
Temp ZONE0 40.000 40.000 41.000 42.000 43.000 43.000 44.000 2.000 3.000 0.745 41.919 °C
Temp ZONE1 35.000 35.000 36.000 37.000 39.000 40.000 40.000 3.000 5.000 1.227 37.258 °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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