Page 2 - Vibrations-2
P. 2
Brief discussion on statistics
Needed for analysing noise.
Mean or average, given a set of numbers {xi}, the mean is
=−1
1
̅ = ∑
=0
Mean squared is given by,
=−1
1
̅̅̅ ∑
2
2
=
=0
Variance, which is measure of the spread of the numbers
in the set {xi} is given by,
=−1
1
2
2
= ∑ (̅ − )
=0
The standard deviation if given by,
2
= √
The normal distribution function is given by,
1 − (̅−) 2
() = 2 2
√2 2
This is expressed in the form so that,
1
