Agilent Technologies InfiniiVision 3000 X-Series User Manual page 227

14
Measurements
The following figure graphically shows the mean and standard deviation.
Standard deviation is represented by the Greek letter sigma: . For a
Gaussian distribution, two sigma (± 1 ) from the mean, is where 68.3
percent of the measurement results reside. Six sigma (± 3 ) from is where
99.7 percent of the measurement results reside.
-3σ -2σ -1σ 1σ 2σ 3σ
The mean is calculated as follows:
∑
=1
¯ =
where:
• x = the mean.
• N = the number of measurements taken.
• x = the ith measurement result.
i
The standard deviation is calculated as follows:
2
∑
( − ¯ )
=1
=
where:
• = the standard deviation.
• N = the number of measurements taken.
Agilent InfiniiVision 3000 X-Series Oscilloscopes User's Guide 227