Keysight DSOX3012T, User Manual

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256 Keysight InfiniiVision 3000T X-Series Oscilloscopes User's Guide
15
Measurements
The following figure graphically shows the mean and standard deviation. Standard
deviation is represented by the Greek letter sigma: σ . For a Gaussian distribution,
two sigma (± 1 σ ) from the mean, is where 68.3 percent of the measurement results
reside. Six sigma (± 3
σ
) from is where 99.7 percent of the measurement results
reside.
The mean is calculated as follows:
where:
• x = the mean.
• N = the number of measurements taken.
• x
i
= the ith measurement result.
The standard deviation is calculated as follows:
where:
•
σ
= the standard deviation.
-2σ
mean
-1σ 1σ 2σ
68.3%
-3σ
95.4%
99.7%
0 3σ
x
¯ =
∑
i =1
N
x
i
N
σ =
∑
i =1
N
( x
i
− x
¯
)
2
N