X∼Bern(P) P(X=1)=p P(X=0)=1−p X \sim Bern(P) \;\; P(X=1)=p \;\; P(X=0)=1-p \;X∼Bern(P)P(X=1)=pP(X=0)=1−p Support k∈{0,1}k \in \{0,1\}k∈{0,1}
P(X=xk)=pk E(X)=∑ixkpkP(X=x_k)=p_k \;\; E(X)=\sum\limits_{\substack{i}}x_kp_kP(X=xk)=pkE(X)=i∑xkpk
E(X)=1⋅p+0⋅(1−p)=pE(X)=1 \cdot p + 0 \cdot (1-p) = pE(X)=1⋅p+0⋅(1−p)=p
Var(X)=E(X2)−E(X)2Var(X)=E(X^2)-E(X)^2Var(X)=E(X2)−E(X)2
E(X2)=12⋅p+02⋅(1−p)=pE(X^2)=1^2 \cdot p + 0^2 \cdot (1-p)=pE(X2)=12⋅p+02⋅(1−p)=p
Var(X)=E(X2)−E(X)2=p−p2=p(1−p)Var(X)=E(X^2)-E(X)^2=p-p^2=p(1-p)Var(X)=E(X2)−E(X)2=p−p2=p(1−p)