P(A) P
A
A
x
2
x2
P(A|B)
P
A
P
P
P
B
P
P
P
P
X
E(X)
P
P
Var(X)
B(n, p)
r = 1, 2, 3, …
Geo(p) Geo(p)
pr = p(1 – p)r – 1
X
1
x1
x1
1
n
nq > 5
np > 5