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What is the Var(X) of a Bernoulli Distribution
p(1-p)
Cov(X,Y)
E[(X−E[X])(Y −E[Y])]
Cov(X, Y) (Alternate expression)
E [XY] − E [X] E [Y]
Var(X+Y)=
Var(X)+Var(Y)+2Cov(X,Y)
Correlation coefficient P(X,Y)=
Cov(X,Y)/ sqrt(Var(X)Var(Y))
Var(Y)/a²
P(|Y−E[Y]| ≥ a) ≤
Var(X) =
E[(X-E[X])²]
Sn²=
n/n-1*(Var(X))
(AnB)u(CnD) =
(AuC)n(BuD)
To divide items amongst things
C(n+r-1)_(r-1)
Number of ways you can order n items
N!
Number of ways you can order c1,c2,….,cn objects into groups
n!c1!c2!…cn!
Orders of n objects of which n1 are indistinguishable
n1 objects of which n2 are indistinguishable
.
.
.
nr-1 of which n are indistinguishable
n!/n1!n2!…nr!
How many distinct ordered sets of length r can be formed from n distinct objects
Pn_r = n!/(n-r)!
A’nB’
(AuB)’
(AnB)’
A’uB’