Normal distribution

Creator
Creator
Seonglae Cho
Created
Created
2020 Aug 23 13:6
Editor
Edited
Edited
2024 Nov 19 12:7
Refs

Gaussian Distribution, Univariate Gaussian

f(x)=ex2,f(x)=12πex22f(x) = e^{-x^2}, f(x) = \frac{1}{\sqrt{2 \pi}} e^{-\frac{x^2}{2}}
Only 2 or 1 (σ\sigma) parameter can represent gaussian distribution. So we don’t loss resolution
Normal distribution 폐쇄성은
Probability Density Function
끼리 곱하거나 적분하거나
Convolution
or Random variable 선형결합해도 가우시안이다. (not random variable for multiplication such as
chi Square Distribution
)
If δ\delta approximate 0, the normal distribution goes to
Delta function
  • DD is dimension of xx
f(x)=12πσ2e(xμ)22σ2f(x) = \frac{1}{\sqrt{2 \pi \sigma^2}} e^{-\frac{(x - \mu)^2}{2 \sigma^2}} N(μ,σ2),N(μ,Σ) N(\mu, \sigma^2) , N(\mu, \Sigma)
Normal Distributions
 
 
Normal Distribution Notion
 
 

Expectation

E[X]=xfμ,σ2(x)dx=yf0,σ2(y)dy+μ=μ. \mathbb{E}[X] = \int x f_{\mu, \sigma^2}(x) dx = \int y f_{0, \sigma^2}(y) dy + \mu = \mu. 

Variance

 V(X)=E[(XE[X])2]=E[X2]μ2.  \mathbb{V}(X) = \mathbb{E}[(X - \mathbb{E}[X])^2] = \mathbb{E}[X^2] - \mu^2. 
 
 
 

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