Devoir libre n12: Variables aléatoires réelles finies. BCPST1 C Pour le 01/06 2011/2012

N r N −r0<
r6N
X
X
N= 4 r= 1
N= 4 r= 2
r= 1 X
r=N
1< r < N
X
k
k−1
r−1
P(X=k) = k−1
r−1
N
r
N
X
k=rk−1
r−1,
N
X
k=rk
r,
N
X
k=rk+ 1
r+ 1.
nn−1
p−1=pn p
E(X) = r(N+ 1)
r+ 1 .
EX(X+ 1)V(X)