Agilent Technologies InfiniiVision 3000 User Manual page 224

14
Measurements
The following figure graphically shows the mean and standard deviation.
Standard deviation is represented by the Greek letter sigma:
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.
The mean is calculated as follows:
where:
• x = the mean.
• N = the number of measurements taken.
• x
The standard deviation is calculated as follows:
where:
•
• N = the number of measurements taken.
224
mean
-3σ -2σ -1σ
68.3%
95.4%
99.7%
∑
=1
¯ =
= the ith measurement result.
i
∑
( − ¯ )
=1
=
= the standard deviation.
0 1σ 2σ 3σ
2
Agilent InfiniiVision 3000 X-Series Oscilloscopes User's Guide
. For a