# lec3

Data Analysis
     
  
  
Some brief recalls from last time
  i   xi Rp   X
          wi=/n
A step of preproccessing is often applied to the data that might be :
       
       

Normalisation
 
¯
xj=
nPn
i=xij      j   j X
yij =xij ¯
xj         Y
           
¯
yj=
n
n
X
i=
yij =

Normalisation
 
s
j=
nPn
i=(xij ¯
xj)     j   j X
zij =xij¯
xj
sj         Z
       Z       
    
¯
zj=
n
n
X
i=
zij =,var(zj) =
n
n
X
i=
(zij ¯
zj)=

Example
    

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